Garman.] 172 [November 4, 



taken from a dissection of a young Mustelus canis, made by a couple 

 of lady pupils of the Anderson School of Natural History. Re- 

 peated observations confirmed the fact in different genera {Mustelus, 

 Odontaspis, Carcharias, Zygcena). Mr. Paulus Roetter, artist in the 

 Museum of Comparative Zoology, kindly made an excellent series of 

 drawings, including the young and adult, male and female, of all the 

 species we were able to obtain; these are soon to be published in a 

 joint paper with Prof. Putnam. The extremities of the oviducts of 

 the adult fertilized female of our Mustelus present quite a different 

 appearance from those of the young. In the virgin they are closed, 

 or with a minute pore-like opening, and extend along the dorsal side 

 of the cloaca to a point opposite the middle of the vent ; in the adult, 

 after fertilization, they are open, as if an inch or more had been cut 

 off the end, and the intestine . opens into the cloaca between their 

 openings and the external. In those specimens of Mustelus under 

 observation, the ovary on one side only was developed, the other 

 being abortive. Amongst those species having round claspers which 

 taper to a point, the minute opening into the ducts of the young 

 female is usually a round pore ; in those having flat ones with rounded 

 ends the pore becomes a short horizontal slit. Those species which 

 have claspers with harsh, sharp edges and hooks, have the posterior 

 portion of the ducts and cloaca very thick and leathery. 



On each side of the vent, extending back upon the ventrals, adult 

 females of the Rajce have close-set patches of shagreen-like scales, 

 which serve as a protection from the claspers of the male. These 

 seem most prominent in those about to deposit the eggs. They are 

 not found in the males. Upon the adult males there are near the 

 outer border of the pectorals two or more rows of long pointed hooks, 

 directed toward the base of the tail; these are capable of. erection, 

 and when retracted are hidden in the grooves beneath them . Here- 

 tofore the nature and use of these hooks has not been clearly ascer- 

 tained. 



On consideration of the structure and motions of the skate, one is 

 driven to the conclusion that their purpose is to aid in coupling ; that 

 it is with them that the male is enabled to hold and turn the female 

 so that their ventral surfaces shall be together. If the males, with 

 their eyes on the dorsal side, were without these hooks, and obliged 

 to turn themselves over, the females, unimpeded in their flight, would 

 easily elude them , but if the female be turned over she is, by means 

 of these hooks, at once detained and placed in a favorable position. 



