644 PEOF. W. A. HEEDMAN S EETISED 



Suborder II. KEMIMYABIA, Herdman, 1888. 



Free-swimming pelagic forms which exhibit alternation of 

 generations in their life-history, and ia the sexual condition form 

 temporary colonies. 



The body is more or less fusiform, with the long axis antero- 

 posterior, and the branchial and atrial apertures nearly terminal. 



The test is well developed. 



The musculature of the mantle is in the form of a series of 

 transversely-ruaning bands, which do not form complete and 

 independent rings, as in the Cyclomyaria. The branchial and 

 peribranchial cavities form a continuous space in the interior of 

 the body, opening externally by the branchial and atrial apertures, 

 and traversed obliquely from the dorsal and anterior end to 

 the ventral and posterior by a long narrow vascular band which 

 represents the dorsal lamina, the dorsal blood-vessel, and the 

 neighbouring part of the dorsal edge of the branchial sac of ati 

 ordinary Ascidian. 



The alimentary canal is placed ventrally. It may be either 

 stretched out, so as to extend for some distance anteriorly, or, as is 

 more usual, be concentrated to form, along with the reproductive 

 organs, a rounded opaque mass near the posterior end of the 

 body, known as the visceral mass or " nucleus." 



The embryonic development is direct, no tailed larva being 

 formed. 



This suborder includes two very distinct families, the Salpidae, 

 which contains the typical members of the group, and the Octa- 

 cuemidse, including a single very remarkable form {Octacnemus 

 bythius, Moseley), which in some respects does not conform with 

 the characters given above. 



Family I. SALPIDJE, Forbes, 1853. 



Body not attached, elongated ; branchial and atrial apertures 

 at the opposite ends. 



Test well developed, gelatinous or cartilaginous. 



Mantle with well-marked muscle-bands, which, however, do 

 not form complete rings, but are wanting ventrally. 



Branchial and peribra^ichial cavities forming a large central 

 space opening to the exterior at both ends. Side walls of branchial 

 sac not developed. At most only a few imperfect or rudimentary 

 stigmata found along the dorsal edge. 



