1877.] 199 [Garman. 



to the remaining orders, the Galeodes (Sharks) and the Batides 

 (Skates and Rays). 1 



For propelling power the Chimserge depend upon the pectorals and 

 ventrals instead of the caudal, as the Galeodes, or the pectorals alone, 

 as the Batides. This use of the ventrals, calling for great freedom 

 of motion as well as support for large strong muscles, is accompanied 

 by a form of pelvis quite different from that of either of the other 

 orders. The pelvic girdle is in two portions, which are loosely joined 

 by ligament in front of the vent. In each half what corresponds to 

 ilium, ischium and pubis is a single broad cartilage with a stout 

 tapering process (the ilium) from its outer posterior angle extending 

 up the side of the body. Near this latter, on the hinder margin, is 

 the articulation of the basal cartilage of the ventral, to which in turn 

 is articulated the base of one of the penes. In front, on the pubic 

 border in the males of Chimaera and Callorhynchus, there is a stout 

 broad piece of cartilage which is so hinged as to fold backward into 

 a concavity on the lower side of the pelvis, in which it rests covered 

 by a band of muscle and the skin. There is a narrow longitudinal 

 opening into this receptacle through which the cartilage is erected. 

 On the inner margin and outer side of the latter there are sharp 

 teeth-like hooks which enable it the better to serve its purpose as a 

 holder in time of coupling. The only motion of which it is capable 

 is outward and downward from, and back into, the cavity. A heavy 

 longitudinal muscle rests on the upper side of the pelvic cartilage, 

 having a tendon which passes over the rounded front margin and is* 

 attached to the outside or back of the holder. By this means the 

 latter is thrown outward from its receptacle when in use. The male 

 also bears a clubbed thumb-like holder on the forehead, between the 

 eyes and snout. On the lower side of the ball this thumb is thickly 

 set with strong sharp teeth, by means of which the pectoral fins of 

 the female can be firmly held when caught between it and the head. 

 When held in this manner the male has his snout under the fin, and 

 is able to hold and turn the female, as is done by the male skates 

 with the retractile hooks near the margins of the pectorals. 2 Having 

 caught the female in this way, the difference in size between the 

 sexes, the male being shorter, is seen to be just enough to bring the 

 intromittent u claspers " into position when they are erected, turned 

 forward and held by the pubic holders. 



1 Prof. L. Agassiz, Essay on Classification, 1857, p. 187. 



2 Garman, Proc. Bost. Nat. Hist. Soc. xvn, 1874, p. 172. 



