Garman.] 202 [May 2, 



arch; of Acanth^as strong, nearly or quite straight; and of Squatina 

 moderately stout and curving backward. 



Carcharias, Lamna and Alopias represent extremes in one direc- 

 tion, and Cestracion, Odontaspis and Scyllium, more at home near 

 the bottom, are good representatives in the other. 



None of the Galeodes have very prominent lateral or median pre- 

 pelvic processes. The males, unlike those of the preceding order, 

 have neither frontal nor pubic holders, and the forcing apparatus is 

 even more simple than that of the skates ; being here but a simple 

 elongate muscular sac lying upon the muscles along the bases of the 

 posterior rays of the ventral and by a duct connected directly with 

 the groove of the penis. Where the male intromittent organs have 

 an armature of shagreen or hooks it is so arranged as to facilitate 

 introduction and resist withdrawal. 



Though there is much greater variety of form in the order Batides, 

 the plan, and the number and character of the articulations, remains 

 as in the preceding. The shaft is without a symphysis in front of the 

 vent as before, but in some cases it is so much arched backward that 

 with the lateral prepelvic extensions the curve formed is a regular 

 semicircle, and in others it is so much bent forward that with the 

 spine-like median process it has the appearance of the furculum of a 

 fowl. In some there are, in addition to the posterior iliac extensions, 

 anterior developments from the ends of the shaft along the sides of 

 the abdomen, and in others, instead of these lateral prepelvic pro- 

 cesses, there is a median spine extending half or more of the dis- 

 tance to the shoulder girdle. 



Differences of habits or of shape of body are usually accompanied 

 by some difference of form in the pelvis, yet beyond these there are 

 sometimes, in closely allied species, modifications of which the exact 

 signification is not at all apparent. 



Pristis, the Saw Fish, has a pelvis resembling those of the sharks ; 

 it is'depressed, convex in front, and not very large or strong. After 

 excepting this genus, which is somewhat similar to the shark in this 

 portion of its anatomy, the order may be separated into two groups, 

 one of which has the straight pelvis, or the backward curve, compris- 

 ing the Rhinobatidas, the Torpedinidse, the Rajidae, and a portion of 

 the Trygonidas, and another having the forward arch or furculum 

 type, which marks the majority of the Trygonidae, the Myliobatidas 

 and the Cephalopterae. 



The first group is that of the greatest diversity of habits, and, as 



