MALAC0Z0A. APODA. HETEBOBRANCHIATA. 309 



to stones, shells, algee, or other bodies, some however 

 being free. 



SYNOPSIS OF THE ABERDEEXSHIRE SPECIES. 



ORDER I.— APODA HETEROBRANCHIATA. 



Branchiae adherent internally to the tube extending 

 from the upper part of the body to the mouth. 

 I 'Erepos, different or diversiform ; Bpdyx<-a, gills. Blain- 

 ville. 



Family I. — Ascidiina. 



Body enveloped in a thick skin, fixed in a reversed 

 position, and terminated above by two orifices, placed 

 near each other. Name from the genus Ascidia. 



Genus 1. Cynthia. — External sac sessile, fixed by a 

 broad base, coriaceous, with two quadriradiate apertures. 

 Cynthia, a name of Diana. Savigny. 



1. Cynthia tuberosa. — Subovate or hemispherical, 

 cartilaginous, with irregular, rough prominences, greyish- 

 white. Tuber 6sus, with prominences. 



Genus 2. Ascidia. — External sac oval, conical, or cy- 

 lindrical, fixed by a broad base, with the upper aperture 

 octoradiate, the lower sex-radiate. 'Aa-Kidiov, "a small 

 leathern bottle." Linnaeus. 



1. Ascidia Prunum. — Subovate, compressed, or di- 

 versiform, softish, rugose, transparent, hyaline tinged 

 with blue ; the apertures with reddish rays. Prunum, 

 a prune or plum. 



2. Ascidia opalina. — Subovate, or somewhat square, 

 compressed, very dense, cartilaginous, opalo-hyaline or 

 bluish-white; the apertures not coloured. Opalinus, 

 like opal. 



3. Ascidia intestinalis. — Subovate, when extended 

 subcylindrica!, softish, smooth, transparent, hyaline, 



