MAYER: MEDUS/E FROM THE WESTERN ATLANTIC. 9 



CTENOPHOR^. 



MNEMIOPSIS, L. Agassiz, 1860. 

 Mnemiopsis McCradyi,^ nov. sp. 



Figs. 23, 33, Plate 6. 



Specific Characters. — Mnemiopsis McCradyi : This species is closely allied 

 to Mnemiopsis Leidyi, A. Agassiz, but differs from it chiefly in the much 

 greater complexity of the ramifications of the chymiferous tubes within the 

 lappets ; and also in the very decided amber color of the gelatinous substance 

 of the animal. It is also remarkable that in this species the gelatinous sub- 

 stance of the body is of so tough a nature that the creature may be removed from 

 the water by hand without suffering injury. Indeed, we know of no Cteno- 

 phore that is as resistant as this species. The animal is 100 mm. in length, 

 our figures being natural size. There are eight longitudinal rows of ciliated 

 plates. Four of these rows, that extend down the lateral lappets, are about 

 twice as long as are the four others that lead from the apex to the auricles. 

 The body is markedly compi-essed, the broad lateral axis, extending through 

 the lappets, being about twice as great as the auricular axis. (Compare Fig- 

 ures 22 and 23.) The lateral lappets are about as long as the remaining por- 

 tion of the body, and are similar in shape and size to those of M. Leidyi, and 

 much longer than in M. Gardeni. (See A. Agassiz, 1865 ; North American 

 Acalepha), Figures 20, 21 and 22, 23.) The apical sense-organ is found at the 

 bottom of a deep cleft at the aboral pole of the body, and is similar in structure 

 to that of M. Leidyi. The chymiferous tubes that wind through the lateral 

 lappets are of a decided purple color and their ramifications are very complex. 

 The mature ova are similar in appearance to those of M. Leidyi. 



A single perfect specimen of this species was found in Charleston Harbor, 

 South Carolina, September 15, 1897. 



1 This species is named in honor of Professor John McCrady in recognition of 

 his important researches upon the medusae of Charleston Harbor. 



