308 MEMOIRS OF THE CARNEGIE MUSEUM 
cingulum is interrupted on the antero-internal angle by a separate minute conulid. 
No other evidence of a cingulum is present on the internal side of this tooth. The 
external face is broken off. The enamel is slightly mammillated on the internal 
margin of the posterior heel ; otherwise the enamel is smooth. The different tuber- 
cles of the heel are quite solidly fused together, leaving a broad triangular cross- 
valley back of the two posterior cusps. 
The symphysis of the lower jaw is quite heavy, and indicates that the mandibular 
rami in this region were very broad. On the whole the ramus is rather short 
antero-posteriorly and deep vertically. The masseteric fossa does not extend below 
the line of the dentition and is indicated on the jaw fragment to be rather deep. 
MEASUREMENTS. - 
Total length of jaw fragment................cccsccccseeesceeeeeeseceneeeccaececseeeeesceseones 129 mm. 
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Po MoT. Gea nC Eansscerena co bedeapgoddecundaSecon pond bec gascancecoSu cance onuvcobnachoabbarasbocda 43“ 
Length of molar-premolar series, approximately .............:0c0sceeeeeeecseeeeeceeeeeens 100‘ 
+) “premolar series, approximately sense) acne -eeeeccccoeeeeee seen = -arcecsesceerss 46 “ 
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Antero-posterior diameter Of P3..............ceecceeseeceecceeeceetseceeeeeeeevenseeeeeneeeenees U2 
; § antero-posterior 14.“ 
Diameters of P4 
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Ee ‘Mt { antero-posterior RonbAnacrnaccodscsodn 6xcacondd easSadssdece suapsapEsESoecdbos 1165, 68 
cha UiatraTiS Verse ieee ncaa ciare sk eae os eee ere erent ewe ee eee Ts 
* © M, § EXTRINSIC eopnade cogon6 onosG0. 56005000 dncoce cosncnangaddocs aqnagsobooE Leen 
Uetransversere aes: Sie veetrsue cee cosas eee ete ree octane eae 183 8% 
‘ ieMia) san tero-posteni On wenca-cestscce saaecencee esas tees tone oaeeeaeaerene Bp 
Thinohyus (Bothrolabis) siouxensis, n. sp. 
The type of this species is based on a nearly complete skull and lower jaws (No. 
1425, Carnegie Museum Catalogue of Vertebrate Fossils). The specimen was dis- 
covered by Mr. J. Grim, Jr., and was presented by him to the writer. It was found 
in the upper part of the Harrison horizon on the upper Niobrara River, Sioux 
County, Nebraska. he specific name indicates the type locality from which it 
came. 
Some characters of the specimen might be regarded as of generic value, viz., the 
absence of P,*, but it is thought best to await the discovery of more complete skele- 
tal material before a final decision regarding its true affinities is had. 
*The position and shape of the glenoid cavity and the posterior narial opening are similar to those in Platygonus 
leptorhinus Williston. 
