Edwin C. Galbreath

“ In the anterodorsal angle of the rim of the orbit the lacrimal bone rests against the frontal and maxillary bones, where the body of the lacrimal contributes to the formation of the posteromedial wall of the nasolacrimal canal. Only a slight part of the maxillary process of the lacrimal remains on each side.
The premaxillary bone, which constitutes most of the anterior part of the rostrum, is typically heteromyid in shape. The frontal process is long and slender. On the side of the rostrum the premaxillary forms the anterointernal border of the infraorbital foramen. ”

“ The left half of the plastron is relatively complete, lacking only the epiplastron and entoplastron. The left 7th, 8th, and 9th marginals are joined to the plastron at the inguinal buttress, and the right 7th, 8th, and 9th marginals are attached to the fifth costal. The carapace has smooth contours with no keel present, but on the lower half of the costals there are seven or eight ridges, and the remaining surface of the costals and neurals are rugose. The marginals lack ridges, and the posterolateral marginals are not serrated. The anterior end of the carapace has a broad shallow notch. ”

“ Discussion.—Heliscomys tenuiceps shows beyond any doubt that the heteromyid pattern of skull was developed by mid-Oligocene times, and in this species was already undergoing lateral compression. The major change later made in heteromyid skulls is broadening of the dorsal surface of the skull in the interorbital area. ”

“ The greatest allowance possible in estimating the length of C. limnodytes fails to bring the ratio of its breadth to length within the range of Recent specimens of similar size. Data from 96 specimens of Recent Chrysemys picta show that the ratio of length to width is not affected by sex, but that the ratio does vary with the age of the specimen. In young animals the length and width are approximately equal, but with further growth the length becomes relatively greater. ”

“ The nasal is widest anteriorly where it curves downward on the side to meet the anterior projection of the premaxillary bone beyond the incisor. Posteriorly, the two nasals have practically parallel lateral borders much as in Liomys.
The frontal bone dorsally is relatively narrower than in any Recent heteromyid, and closely resembles that of the geomyids. There is a slight depression in the midline of the skull where the two frontals unite, but no evidence of a ridge for the attachment of the temporal muscle. ”

“ Any fossil record of Kinosternon is a welcome find, and these two specimens give new data both as to age and distribution. However, it should be emphasized that these identifications are based on fragments, and are tentative. ”

“ If cusps in H. tenuiceps do form lophs, the process is definitely not by union of the cusps with the anterior cingulum. The transverse median valley is deep and divides the tooth on the buccal side. The anteroposterior valleys are shallow and hanging, and can be said to exist only as indentations between the two sets of cusps. The paracone and metacone are much higher than the other two cusps, but much of this disparity in height may be the result of greater wear on the protocone and hypocone ”

“ The first neural is rounded, and the 2d, 3d, and 4th are hexagonal, with the broad ends forward. Anterior margins of the 2d and 3d neurals are concave, and the anterior margin of the 4th neural is straight. ”

“ No. 5935 is from the Pleistocene of Harper County, Kansas, and No. 7677 is from the early Pleistocene of Beaver County, Oklahoma. Each is composed of costals and neurals which may be referred to this genus. Their size indicates an animal considerably larger than any on record, and probably these specimens represent a new species. ”

“ A slight anterior arm of the internal cingulum may have reached forward to the anterior face of the protocone. Wear prevents knowing whether a crest surrounds the tooth completely, or only on three sides. ”

“ P4 with posteroexternal cusp (metacone) anterior to central (hypocone) and lingual (entostyle) cusps, which are connected by a cingulum; internal cingula of molars undivided, and as high as paracone and metacone; style of each cingulum opposite the straight median valley; rostrum deep and laterally compressed.
Description.—The type consists of the preorbital and interorbital parts of a skull. Its size is comparable to that of the Recent heteromyid, Liomys pictus Merriam. L. pictus is the species referred to in the comparisons below when only the generic name Liomys is mentioned. ”

“ No. 7729 consists of fragments of marginals, costals, and plastronal elements collected from Edson Quarry, Sherman County, Kansas. The age is middle Pliocene (Hemphillian) . No. 7679, consisting of a nuchal, and fragments of marginals, costals, and neurals is from Nye Sink, XI Ranch, Meade County, Kansas, and is of Pleistocene age. ”

“ Femoral scute: Length of border of scute on midline, 24; width of anterior border of scute from midline to inguinal notch, 41; width of posterior border of scute from midline to outer border (along sulcus) , 40; length of outer margin of scute from inguinal notch to femoro-anal sulcus, 46.
Anal scute: Length of margin at midline, 36; length of femoro-anal sulcus, 40.
Remarks.—Noteworthy is the intermediate nature of C. limnodytes when compared with species of the genera Chrysemys and Pseudemys. ”

“ In size the teeth of H. tenuiceps average twenty per cent larger than any of the upper teeth of H. gregoryi, H. hatcheri, or the Pipestone Springs specimen, and exceed any of the known lower teeth including those of H. vetus and H. senex by twenty-five per cent or more. ”

“ Length of plastron, 165 (estimated) ; width of plastron, 130 (estimated) ; length of anterior lobe, 45 (estimated) ; width of anterior lobe, 75 (estimated) ; length of posterior lobe, 62; width of posterior lobe, 82; length of bridge from axillary to inguinal notch, 60.
Plates of the Carapace and Plastron
Nuchal: Width of anterior margin, 12 (estimated) ; greatest width, 37 (estimated) ; length at midline, 35 (estimated) .
First neural: Greatest width, 13; length at midline, 17. Second neural: Greatest width, 16; length at midline, 14. Third neural: Greatest width, 18; length at midline, 16. ”