420 CTENOPHOKA 



5. Eucharidae. Euchm-is. 



6. Mnemiidae. Mnemia, Mnemiopsis. 



7. Oalymmidae. Calymma. 



8. Ocyroidae. Ocyroe. 



Most of these Ctenophores occur in the warm and tropical seas ; 

 but Bolina is found occasionally at Plymouth in the month of 

 May, on the west coast of Ireland, and at other stations on the 

 British coasts. JEucharis is regarded as one of the most beautiful 

 of the Phylum. A swarm, some miles in length, of large speci- 

 mens of E. multicornis was met by the Plankton Expedition in 

 the south equatorial current of the Atlantic during the month 

 of September. 



Order III. Cestoidea. 



In this order the body is so much compressed in the trans- 

 verse plane and elongated in the sagittal plane that it assumes 

 the shape of a long narrow band or ribbon. The tentacular 

 sheaths are present but the tentacles are degenerate in the adult. 

 The tentacular functions are performed by numerous tentilla 

 situated in long grooves extending along the whole length of the 

 oral side of the band-like body. The transverse ribs are reduced ; 

 the sagittal ribs extend along the whole of the aboral side. 



Fam. Oestidae. — This is the only family of the order. 

 Cestus veneris, the Venus's girdle of the Mediterranean Sea, is 

 also found in the Atlantic Ocean, and specimens belonging to the 



Fig. 182. — Cestus pectenalis. ^i, aboral sense-organ ; 0<, the sagittal ribs ; 

 M, mouth. (After Bigelow.) 



same genus, but probably to a different species, occur as far north 

 as the White Sea. Some of the larger specimens are consider- 

 ably over 1 metre in length. 



C. pectenalis was found in abundance off one of the Maldive 

 Islands,^ and differs from C. veneris in having a large and pro- 

 ' H. B. Bigelow, Bull. Mus. Comp. Zool. xxxix. 1904, ]>. 267. 



