NO. 228U. THE NEW COPEl'OD FAMILY SPHYRIIDAE— WILSON. 559 



this stage (fig. 30) a complex system of dilator muscles riimiing for- 

 ward and backward from the junction of the genital segment and 

 abdomen to the sides of the barrel-shaped rectum. These indicate 

 that the rectum takes an important part in respiration during early 

 development. But although the rectum is retained in the matured 

 adult and increases in size with the growth of the rest of the in- 

 testine, these dilator muscles do not increase accordingly. They be- 

 come restricted to that part of the rectum contained in the abdomen, 

 and when the latter is finally reduced almost to nothing these muscles 

 are too weak to accomplish much. 



There are no muscles connected with the first antennae in any 

 female thus far examined, but the second antennae show a well de- 

 veloped musculature. The presence of corresponding muscles in two 

 spherical processes on the head of Rebelula indicates that these 

 processes are really the remains of the second antennae, because the 

 other cephalothoracic processes do not possess muscles. 



In Paeon there are very strong muscles connected with the second 

 maxillae, while the musculature of the maxillipeds is weak and prac- 

 tically useless. In Sphyrion., on the contrary, the musculature of the 

 second maxillae is comparatively weak, while that of the maxillipeds 

 is much stronger, although relatively not as strong as in the maxillae 

 of Paeon. 



The muscles connected with the swimming legs of the larva en- 

 tirely disappear in the adult. 



The body muscles of the female are separated naturally into two 

 sets, the longitudinal and the dorso-ventral muscles. The longitu- 

 dinal muscles are very similar to those of the Lernaeopodidae, with 

 certain minor variations. On the dorsal surface there are four bands 

 of muscle, two on either side of the median line, running the entire 

 length of the body from the base of the dorsal cephalothoracic proc- 

 esses to the anterior margin of the abdomen. In Paeon ferox and in 

 Sphyrion and Rebelula the two inner bands are separated a little in 

 the trunk, leaving an open space along the median line over the in- 

 testine. In Paeon versicolor they remain close together, but the two 

 outer bands are removed nearly or quite to the lateral margin of 

 the trunk. 



On the ventral surface are four wide bands, two on either side, 

 which run similarly from the base of the maxillipeds to the anterior 

 margin of the abdomen. All four of these remain close together 

 throughout their entire length in Paeon versicolor and in Sphyiion 

 and Rebelula^ but in Paeon ferox the two outer ones are removed to 

 the lateral margins of the trunk. Consequently in Paeon ferox there 

 are two median dorsal bands separated by a narrow interval, two 

 median ventral bands and two bands on each lateral margin of the 

 trunk. In Paeon versicolor there are two median dorsal bands, not 

 62055— 20— Proc.N.M.vol.55 37 



