310 MALACOZOA. APODA. HETEROBRANCHIATA. 



greenish-grey, or bluish-green, the orifices with red spots. 

 Litest bidlis, like a piece of gut. 



ORDER I.— APODA HETEROBRANCHIATA. 



Branchiae varying in form, but always contained in 

 the tube leading from the posterior or upper part of the 

 body to the mouth j the body anomalous or irregular in 

 form, enveloped in a strong sac, perforated with two 

 apertures, and destitute of shell, external or internal ; 

 the mouth situated in the interior, destitute of labial 

 appendages. 



Family I. — Ascidiina. 



Body diversiform, enveloped in a thick, more or less 

 rugous, contractile skin, adherent or fixed in a reversed 

 position, or with the mouth downwards, at the other or 

 ujiper extremity terminated by two tubes or orifices, 

 placed not far from each other ; the upper larger orifice 

 leading to the branchial cavity, at the lower part of 

 which internally is the mouth, the other aperture leading 

 to the tube continuous v.ith the termination of the in- 

 testinal canal and that of the f^enital or.f^ans ; the bran- 

 cliiae, which are equal and broad, expanded like a net- 

 work on the inner surface of tlis two lateral valves of 

 the branchial cavity, its orifice furnished internally with 

 a denticulate membranous ring, or a circle of filaments. 



Genus 1. Cynthia. 



Body sessile, fixed by a broad basis in a reversed 

 position ; outer sac cartilaginous or coriaceous, with two 

 quadriradiate apertures ; inner sac coriaceous ; branchial 

 cavity longitudinally phcate, its reticulations without 

 papillae j abdomen lateral ; ovaiy multiple. 



