GARMAN : THE CIIIMAEROIDS. 265 



liuc 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 Rhinoclii- 

 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 3d° 44' 30" and west longitude 70° 30' 45" at a depth of lOSl 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 jiroboscis, 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 a more ])roininent 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 3 and 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 10 tritors 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. 



Xumber 35520 of the National Museum collection is a young male of about 

 4.1 inches in length; it was ca])tured at a depth of 991 fathoms in north lati- 

 tude 39° 3 7' 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 



