422 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxin. 



length of the carapace) ; its posterior sinus is vevj broad, with a 

 squarely truncated base, while the posterior lobes are narrow and 

 short. The abdomen projects nearly its whole length beliind the 

 sinus of the genital segment, and is plainly visible in dorsal view. 

 The sixth segment plate has only just started, and covers less than 

 half the dorsal surface of the abdomen. Anal laminae of the same 

 pattern as in other genera of this subfamily, narrow and long, each 

 tipped with four plumose setae. Appendages like those of the adult 

 with the exception of the foiu'th swimming legs, in which the rami are 

 much smaller, less laminate, and the exopod is armed with claws 

 similar to those on the third legs, and is indistinctly jointed. The 

 fourth endopod, however, even at this early stage is wholly devoid 

 of spines or- setae, and shows no signs of segmentation. 



The Naupliushas already been described on page 336; owing to the 

 inability of the female to move about when placed in an aquarium, 

 the eggs always die unless they were just on the verge of hatching when 

 obtained. This makes it difficult to secure the nauplii, and explains 

 how it happens in a genus as common as Pandarus that they have not 

 been seen and described oftener. 



This species was first described by Say in 1817, fro in specimens 

 taken from the dog-fish, Squalus canis Mitchill, and preserved in 

 the cabinet of the Academy of Natural Sciences in Philadelphia. 

 The original description was brief and lacked many details, but 

 enough was presented to identify the species, and the missing details 

 were supplied in an excellent description given l)y Rathbun in 1884. 

 But neither author found the male, and that sex is here presented for 

 the fii'st time, together with additional information upon the anatomy 

 of the female. The abundance of the species upon the sharks common 

 along our Atlantic coast is proven by the following list of the specimens 

 in the U. S. National Museum. Most of these were found upon the 

 fuis of the sharks, attached in such a way that the egg-cases would 

 float free from the margin of the fin in the clear water (fig. 1). 

 Hence the Pandarus always has its head toward the head of the 

 shark; when more than one are found on the same fin they are attached 

 side by side and strictly parallel, often as many as eight being found 

 on one side of a single fin, and as many on the other side. Usually 

 these females have algae and protozoa of various kinds growing upon 

 their carapace and dorsal plates; these are fastened to the margins 

 and angles of the plates and float back in the water around the egg- 

 strings. 



Often the female will be so completely covered that none of the 

 dorsal surface can be seen (fig. 1 ) . The fins most commonly chosen 

 are the dorsal, the anal, and the ventral. Specimens are less often 

 found on the pectorals or the tail. 



