92 Universiti/ of California Fublicatioiis i)i Zoology [Vol. 11 



to 2.83 per cent of total length of animal. Form approximately 

 triangular, the position of greatest width being opposite the 

 rounded obtuse angle in the caudal fourth of the fin. 



Posterior fin varies in length from 19.4 to 26.-1, and in width 

 from 2.96 to 5.27 per cent of total length of animal. It ap- 

 proaches but never reaches seminal vesicles, the interval varying 

 from 2.19 to 4.60 per cent of total length of animal. Jlore than 

 50 per cent of fin in front of tail-septum, the extremes of 

 variation being 51 and 61 per cent. Position of greatest width 

 about half way between tail-septum and posterior extremity of 

 fin. Interval from anterior to posterior fin varies from 11.7 per 

 cent of total length of animal in the younger individuals to 

 5.90 per cent in the older ones. 



Vestibular ridge (pi. 2, fig. 2), provided with irregularly 

 rounded papillae, so arranged that one papilla is usually opposite 

 the interval between adjacent teeth. However, some intervals 

 are skipped, so that the number of teeth is greater than the 

 number of papillae, notwithstanding the fact that two or three 

 papillae occur internally to the teeth. One tooth, sometimes two 

 and rarely more, project beyond wing of ridge, the adjacent one 

 usually being well covered by it. Notch covers the external four 

 or five teeth. External process short and blunt, scarcel.y one and 

 a half times longer than broad. 



Anterior teeth (pi. 2, fig. 3), three to seven, usually five or 

 six. They are closely set, with overlapping bases. Very 

 divergent distally. 



Posterior teeth (pi. 2, fig. 2), eight to sixteen, usually ten 

 or eleven. They are closely set and overlapping, though less 

 markedly than anterior teeth. Slightly divergent distally. "While 

 they are nearly of the same width (at the base) as the anterior 

 teeth, they are much longer, the longest anterior tooth being only 

 two-thirds as long as the shortest posterior tooth. 



Seizing jaws (pi. 2, fig. 4), seven to ten, usually eight or 

 nine. Curvature 41 to 51 per cent. Points with an oval base 

 and imbedded from 20 to 25 per cent of their height into the 

 shaft. Top of shaft and base of point converge in approaching 

 edge of jaw. Edge of point nearly straight while the back is 

 considerably curved. Pulp-canal displaced considerably toward 



