MALAC0Z0A. APODA. HETEEOBRANCHIATA. 311 



1 Cynthia tuberosa. Tuberous Cynthia. 



External sac sessile, snbovate, or hemispherical, very dense, 

 cartilaginous, covered with irregular prominences or tubercles 

 of various sizes, its colour greyish-white or grey. It is ter- 

 minated above by a little-prominent aperture, surrounded by 

 irregular radiating hard corrugated obtuse ridges, and presents 

 on the side, about a third down, a prominent wart-like, quad- 

 risulcate, tubercular anal aperture. The substance of this 

 outer tunic is thick, and firm throughout, its inner surface of 

 an opaline white. The inner sac, closely applied to the outer, 

 is ovato-globose, thick, firm, externally smooth, yellowish, 

 toward the upper part carmine ; its branchial aperture rugose ; 

 the anal cylindrical, rather long. Internally, this sac presents, 

 on the branchial surface, eight longitudinal thick, semicylindri- 

 cal ribs, and numerous longitudinal elevated while lines de- 

 cussated by smaller transverse lines, without papilla? at the 

 intersections. This branchial membrane extends to the base, 

 and bears a great resemblance to that of the Actiniae. Its 

 colour is yellow or pinkish. In the abdominal space, the in- 

 ternal surface of the sac is formed of irregular roundish soft 

 prominences of a red colour. The anal tube extremely firm, 

 at the end cartilaginous, with four rugous lobes, and four coni- 

 cal papillae. Length about an inch. 



First found by Miss Isabella Macgillivray in September, 

 1842, having been brought up by a fishing-line from deep 

 water off Aberdeen. 



This, the most extraordinary-looking of our species, presents 

 the appearance of an aggregation of very hard Ascidise, its 

 protuberances being so numerous and prominent, that there is 

 difficulty in finding among them the quadripartite apertures. 

 It is crusted, like the rest, but I have not found Modiolae im- 

 bedded in it. 



Genus 2. Ascidia. 



Body oval, conical or cylindrical, contained in an ex- 

 ternal leathery, cartilaginous, or subgelatinous skin, fixed 

 by its enlarged base, and terminated by two tubes or 

 apertures, the upper with eight lobes or rays, the lower 

 with six ; inner sac smooth ; branchial cavity even, its 

 reticulations papillate ; abdomen lateral ; no liver ; ovary 

 single. 



The Linnsean genus Ascidia has been variously divided 



