677 



4235. The skull of a male Otter (Lutra vulgarid). 



The teeth have been removed from the right side of both jaws, and are separately dis- 

 played ; their nature is indicated by their symbols. The small upper p 1 has no homotype 

 in the lower jaw ; the double-fanged tooth which opposes and even advances a little beyond 

 it answers to the double-fanged p 2 in the upper jaw, and the number of the molar series is 

 rendered the same in both jaws by the additional true molar (m 2) in the lower one. This 

 will be clearly understood by comparing the dentition of the Otter with that of the Marten 

 (No. 4153), for example, in which p 1 is retained in the lower as well as in the upper jaw. 



Hunterian. 



4236. The skull of a male Otter (Lutra vulgaris). 



The calvarium has been removed. A narrow articular surface upon the basioccipital con- 

 nects together the two condyles. The cranial cavity is remarkable for its great posterior 

 expanse and its extreme contraction between the prosencephalic and rhinencephalic divisions. 

 In this example the temporal ridges commencing from the postorbital processes meet at an 

 open angle, and extend backwards, as a low and straight sagittal crest, as far as the broader 

 occipital crest. The zygomatic arches are strong and boldly curved ; they bifurcate ante- 

 riorly to surround the large antorbital foramen. The sella turcica is very shallow and but 

 feebly indicated. The tract for the optic chiasma is very long and narrow. The crista galli 

 extends backwards through nearly the whole of the rhinencephalic fossa. The longitudinal 

 sinus has left a deep groove, and communicates behind with two small venous foramina in the 

 superoccipital bone. 



Hunterian. 



4237. The cranium of a male Otter (Lutra vulgaris), in three transverse sections. 



In the posterior segment the form and relations of the bony tentorium are well seen : the 

 bony plates are continued into the tentorium from the petrosal ridges. Two small venous 

 foramina in the superoccipital open above the tentorium into the termination of the bed of 

 the longitudinal sinus. The middle and anterior sections show the absence of frontal sinuses, 

 and the commencement of the olfactory chamber directly in front of the rhinencephalic fossa, 

 the cribriform plate, or back part of the olfactory capsule, with the coalesced prefrontals 

 separating them. The entry to the nasal passages is almost blocked up by the large and 

 complex turbinals. 



Presented by Prof. Owen, F.R.S. 



4238. The right ramus of the lower jaw of the same Otter. 



4239. The skull of a female Otter (Lutra vulgaris). Presented by Henry Cline, Esq. 



4240. The skull of a female Otter (Lutra vulyaris). Hunterian. 



