Fam. Cephalodiscidae. 



Cephalodiscus Mliuosh. 



Zooids secreting a gelatinous coenoecium formed of numerous lamellae. C o e n o e c i u m 

 with a continuous cavity or with a separate cavity for each zooid, each orifice produced into 

 one or more peristomial processes. Zooids consisting of proboscis, collar, and metasome. 

 Proboscis greatly flattened in an antero-posterior direction, its anterior wall mainly composed 

 of a high, glandular epidermis, and provided with a curved, transverse pigment-band, with 

 dorsal concavity. Body-cavity of proboscis single, opening to the exterior by two symmetrically 

 disposed proboscis-pores, which lie on either side of a median pericardium. Collar with an 

 anterior free edge, the dorsal part of which is split up to form 4 — 6 pairs of tentaculiferous 

 arms, between the bases of which is the central nervous system ; while the ventral i)art forms 

 a simple lower lip, operculum, or post-oral lamella. Body-cavity of collar paired, with complete 

 dorsal mesenter\-, which supports a pharyngeal outgrowth ("notochord") passing forwards along 

 the septum between the proboscis-cavity and the collar-cavities. These open to the exterior by 

 a pair of collar-canals, immediately behind which is a jKiir of gill-slits situated in the septum 

 between the collar-cavities and the metasomatic cavities. Metasome, body or trunk 

 elongated at right angles to the antero-posterior axis of the zooid, containing the gonads and 

 nearly the whole of the alimentary canal. Anus and generative apertures situated dorsally on 

 the metasome, which is produced ventrally into a muscular stalk, from the distal end of which 

 originate buds. Body-cavity of metasome paired, with complete or incomplete dorsal and ventral 

 mesenteries. Sexes dimorphic. 



It will be seen that the generic diagnosis, as above given, includes all the most important 

 features which have previous!)- been described in C. dodecaiop/uis. The specific characters are 

 in fact subordinated to the striking assemblage of anatomical peculiarities which have already 

 been recognized in the type-species. The curiously reduced males of C. si/n[<;'ae have not, 

 however, been shewn to possess proboscis-pores, gill-slits or operculum, while the arms are 

 reduced to a single pair, and bear no tentacles. 



C. dodecalopJms M'Intosh. (PI. 11, fig. 21. PI. I\', fig. 42, etc.). 



C. dodecalophus .M'liUosh (82, 83, 87J, Lankester (85), Lang (90), Spengel (93, pp- 721, 753). 

 Masterman (97, 98, 03), Cole (99). 



Straits of Magellan. "Challenger" Collection. 448 M. 



Female colony. 



Coenoecium large, reaching a length of at least 225 mm., its cavity continuous, opening 

 at intervals by irregularly arranged orifices, whicli may bear two or more long peristomial 

 processes. Metasome ovoid '), giving off the stalk from its anterior surface. Stalk thick, .short 



i) The material was, in all the species, preserved without special precautions being taken to obtain the zooids in an extended 

 condition. There is clear evidence, in most cases, that the greater number are in a highly contracted state, and it is this condition to 

 which the diagnoses refer. 



