WKLLBURX : OX THE OCCURRENCE OF STREPSODUS SULCIDEXS. 87 
line between the two being indicated by a sutural line which 
runs downwards and backwards from a point immediately behind 
the first laniary tooth to cut the inferior edge of the jaw at an 
acute angle. Above tliese runs tlie dentary bone, which — with 
the exception of a portion of the deep fore-end or symphysis — 
is mostly covered b}' the strong, thick laniary bones, Avhich 
appear to be firmh^ anchylosed to it, although there is plain 
evidence at tlie posterior end— where the bone is broken across 
— that the bones were originally developed in separate centres of 
ossification. Three of these laniary bones are shown, that at the 
symphysis being the largest : in position they run in a line, from 
before backwards, a short distance below the dentary edge of the 
dentary • bone, and each bears a strong laniary tooth, of which 
the second and tliird show the usual characters, viz. : — They are 
robust, elongated, somewhat flattened, apex straight, fine stria? 
on i)iner surface, base broad and sliowing vertically elongated 
depressions extending a short distance beyond the basal furrows. 
The anterior laniary at tlie symphysis is a larger and more 
powerful tooth than the others, it sliows characters similar to 
those of the other teeth with the exception that they (the 
characters) are more strongly marked, especially the vertically- 
elongated depressions at the base, and the aj^ex, instead of being 
straight, is strongly and evenly bent backwards and slightly 
inwards, this being a point of interest, as in the specific diagnosis 
the apex of the teeth are given as being straight. 
Form and locality : Better Bed Coal Shale, Lower Coal 
Measures, Low Moor : and Barnsley Thick Bed Coal Shale, 
Middle Coal Measures, Barnsley ; both in Yorkshire. 
EXPLAXATIOX OF PlaTE XVIII. 
Strepsodus sulcidens Handcock and Atthey. Mandible seen from 
inner side. S.Mn. — Symphysis of dentary bone. S. L. 
— Symphysical laniarv tooth. L.T. 2 and L.T. 3. — 
Second and third laniary teeth. L.B. 1 and L.B. 2. — 
Laniary bones. ID.— Infradentaries. Specimen in the 
Brighouse Museum, Yorkshire. 
