REPORT ON THE TUNICATA. 83 



fig. G). The series A are by far the largest, and are usually much branched. The membrane 

 on their posterior (branchial) surface is loose and voluminous (PI. VI. fig. 7, tn. m.). 



The dorsal tubercle (PI. VI. fig. 9) is very simple, and approaches in structure that 

 of Mohjiiht pyrifonnis (PI. VI. fig. 3). The duct from the neural gland swells out at 

 the posterior angle of the peritubercular area into an elongated oval chamber, which 

 opens anteriorly by a simple quadrangular mouth. 



Three specimens of this species were obtained at Kerguelen Island. One is labelled 

 " Kerguelen, 10-60 fathoms;" one " January 29, 1874, off London River, Kerguelen, 

 100 fathoms; " and one " Kerguelen, 10-100 fathoms." 



Family Cynthiid^;. 



Body usually attached, rarely free, sometimes pedunculated. 



Test membranous or coriaceous, rarely cartilaginous or covered with sand. 



Branchial aperture four-lobed, atrial four-lobed. 

 Branchial Sac longitudinally folded ; internal longitudinal bars not papillated ; 



stigmata straight, never formiug spirals. 

 Tentacles simple or compound. 



Intestine on the left side, slightly or not at all attached to the mantle. 

 Genitalia on the inner surface of the mantle, either on both sides or on one only. 



The Cynthiidse, and especially those forming the sub-families Bolteninse and 

 Cynthinas, which have compound tentacles, are not far removed from the Molgulidse, and 

 were only separated as a distinct family by Lacaze-Duthiers in 1877. Heller previously 

 (1874-77) considered them as one family. The Cynthiidae form a very large group, and 

 contain probably more known species than the other three families of Ascidias Simplices 

 put together. 



Savigny, in 1816, 1 founded two of the genera comprised in this family, namely Boltenia 

 and Cynthia. The latter genus as defined by Savigny may be split up into two well- 

 marked sections — one containing the typical forms (the modern Cynthia), in which there are 

 many folds in the branchial sac and the tentacles are compound ; and the other including 

 the Styela-like forms with only four folds on each side of the sac and simple tentacles. 



As each of these three types has been split up into genera I have thought it best to 

 consider them as sub-families, and they were described in the Preliminary Eeport 2 

 as the Cynthime, the Bolteninas, and the Styelinse. 



The condition of the apertures though rather variable is quite characteristic ; there are 

 never more than four well-marked lobes round either branchial or atrial apertures. 



1 Mi imoires sur lea Animaux .sms Vertebres, pt 2, fasc. 1. 



2 Proc. Roy. Soc. Edin., Session 1880-81, p. 53. 



(ZOOL. CHALL. EXP. PART XVII. — 1882.) R 12 



