GARMAN: THE CHIMAEROIDS. 265 
line suddenly drops to the lower edge of the muscular portion of the tail where 
it continues to the end. The line is similar in structure to that of Rhinochi- 
maera pacifica, as figured on Plate 4, Fig. 3; it is an open groove with closely- 
set ribs, which do not quite meet over the cavity. The aural portion of the 
line bends forward at each side from the lateral, and passing inward turns 
sharply back to meet its fellow in an acute angle, with the apex backward, 
from which a short line is extended farther backward toward the dorsal spine. 
Specimen 39415 of the National Museum is a female, taken in north lati- 
tude 39° 44’ 30” and west longitude 70° 30’ 45” at a depth of 1081 fathoms. 
Its measurements are: total length, 25; length of head, 6; length of snout to 
mouth, 4; snout to vent, 10.5; snout to dorsal spine, 6.5; snout to anal, 14.25; 
snout to end of second dorsal, 14.25; length of dorsal spine, 2.75; length of 
pectoral fin without base, 4.5; length of ventral fin, 2; depth of body between 
dorsals, 2.75 ; width of pectoral, 2.75 ; width of ventral, 1.5 ; depth of tail, 1.4 ; 
width of proboscis, 1.1; depth of orbit, 0.56; length of orbit, 0.75; and length 
from snout to beginning of the upper fin on the tail, 14.9 inches. The dorsal 
spine has sharp retrorse denticles on both of the hinder edges, and it has longi- 
tudinal striations along its sides. It has a smooth, rather sharp ridge in 
front, and close behind this in a transverse section it is concave and then slightly 
convex. The spine has amore prominent anterior ridge and more distinct 
_denticles than on the young, but it is stouter in proportion to the fin on the 
latter. The tongue is subtriangular, Plate 5, Figure 5, and it has a peculiar: 
structure, induced by feeding habits in connection with which its most im- 
portant function may be performed in sorting out. the softer tissues from the 
harder portions or broken shells of the prey. The teeth show a considerable 
advance from what obtains on 35631, as shown in Plate 5, Figures 6 and 7. 
In the outlines the hindmost angles are sharper, from extension backward 
on the edge of the jaw, and the tritors are broader, longer, and closer together, 
Plate 5, Figures 3and 4, They have expanded until those posteriorly on the 
median ridge have come to resemble the dental cards of species of Mylio- 
batis to which they suggest a similarity also in feeding habits. Possibly the 
tritors coalesce and their dividing lines become obliterated in greater ages, 
for this would be in line with the development traced through 35520 and 
35631 to the present specimen; in one the tritors are merely suggested, in 
another they are well grown but separated, and in still another they are much 
enlarged and in contact, Plate 5, Figures 3-9. Each of the vomerine teeth 
hooks downward in front and has 9 or 10tritors on its cutting edge. There 
are three series of tritors on each palatine and but two on each mandibular 
tooth, Plate 5, Figures 3 and 4; in this they differ from what obtains on the 
teeth of 35631, Plate 5, Figures 6 and 7, a difference which may be due to 
coalescence of tritors on the older individual. 
Number 35520 of the National Museum collection is a young male of about 
4.1 inches in length; it was captured at a depth of 991 fathoms in north lati- 
tude 39° 37’ 45” and west longitude 71° 18’ 45’. The specimen was secured 
near the time of extrusion from the eggshell, and so marks a depth at which 
