114 SELACHINEMA 



unequal halves of the mandible is a thin, arcuate, toothless element, which ends in 

 an incurved point forming the distal end of the mandible. The chitinous project- 

 ing portion of these jaws is slightly inwardly arcuate: Each jaw is somewhat 

 longer than the head is wide, although the projecting portion is only about half as 

 long as the head is wide. These jaws are permanently extended, and cannot be 

 withdrawn into the pharynx. They are used in a manner somewhat like that of 

 the projecting mandibles of certain insects. It appears as if a dorsal jaw or 

 mandible had been broken away from the only specimen so far seen a young one. 

 There is a circlet of cephalic setae opposite the base of the chitinous, extended por- 

 tion of the jaws. There are six of these setae in one circlet, and behind each of 

 the submedian setae of this circlet there is a smaller seta slightly farther back so 

 that the total number of the cephalic setae may be said to be ten. The length of 

 the six main setae is unknown, as they are all broken away from the only specimen 

 hitherto seen. A restoration of these six main setae is attempted in the illustra- 

 tion; hence these setae are shown by means of dotted lines. The spiral amphids 

 consist of about three and one-half winds, and are nearly half as wide as the head, 

 and are placed opposite the base of the pharynx, their anterior borders being 

 about half as far from the anterior extremity as are the bases of the before-men- 

 tioned naked chitinous portions of the jaws. There are no eye-spots. The phar- 

 ynx is of the form consonant with the strongly developed jaws, that is to say, it 

 is triangularly concave-pyramidal. Its base is rather plainly indicated by the 

 proximal ends of the chitinous roots of the jaws, and lies opposite the posterior 

 borders of the amphids. The oesophagus begins as a tube about two-fifths as 

 wide as the base of the head, and continues to have this diameter throughout the 

 greater portion of its length. It is separated from the oesophagus by a constric- 

 tion. There is no bulb and there does not appear to be any distinct cardia. The 

 intestine, which is made up of cells of such a size that probably four to six are 

 required to build a circumference, is rather thick-walled. The small granules in 

 the cells are of rather uniform size, and do not give rise to any distinct tessella- 

 tion. The rectum appears to be shorter than the anal body diameter. The 

 tail is convex-conoid in the anterior part in such fashion that at a distance from 

 the anus at least as great as the anal body diameter, it has diminished so that it 

 is only about one-eighth as wide as at the anus. Thence onward it is nearly 

 cylindroid, although it still diminishes slightly in diameter. It ends in a slightly 

 swollen terminus bearing a slightly elongated, plain, unarmed spinneret. It 

 seems likely that the tail is prehensile. The caudal glands are located in the 

 vicinity of the anus. The renette cell lies opposite the cardiac constriction, and 

 is somewhat dumbbell shaped, and placed transversely; the slender duct leads 

 forward from it, and connects with the prominent pyriform ampulla, which is 

 one-fourth as wide as the corresponding portion of the neck, and this in turn 

 leads to the excretory pore near by, opposite the nerve-ring. This latter sur- 

 rounds the oesophagus somewhat squarely. In front of the exceedingly incon- 

 spicuous anus there are two lateral rows of seven or eight minute, equidistant 

 pores. These occupy a space about equal to twice the length of the corresponding 

 body diameter. The distance between these small circular organs is three to 

 four times as great as the diameter of one of them. They appear merely to 

 penetrate the cuticle, so that the extejit of their chitinous outlines in a radial 

 direction is about equal to their width. There are three or four similar pores on 



