ASC'IDIA PUSTULOSA. 139 



nearly one-third down the side. Test rather thick, 

 semi-transparent, coriaceous, covered with irregular- 

 sized, warty, or pustulose tubercles, principally on the 

 upper or left side ; these generally bear lesser tubercles 

 or echinations on their surface ; the lower or recumbent 

 side is nearly smooth. Mantle yellowish, blotched with 

 red, especially towards the apertures, and sprinkled 

 with opaque white. Tentacular filament* few and 

 stout. Branchial sat' with rather small papillae. Oral 

 lamina wide, smooth, with the right side ribbed. 



LctKjtii about three inches. 



Hah. Deep water? 



ENGLAND. Fowey Harbour, Cornwall, dredged 

 (Alder). 



SCOTLAND. Firth of Clyde [Lamlash Bay'r] (Ailnunt). 

 First ,-m'd. Alder, 18(33 [; coll. 1847]. 



This species is readily distinguished from J.. uin/fiila 

 by the pustulose tubercles of its test (PI. XVI, fig. 1) 

 as well as by its more ovate form ; in these respects it 

 approaches somewhat to A. amlrata, but it is of much 

 larger size, less echinated, and of a different colour. 

 It has only yet been found in the localities mentioned, 

 and appears to be rare. 



The mantle (PI. XVI, fig. 2) is well supplied with 

 muscles which are not arranged with much regularity, 

 except at the margins from which they extend at right 

 angles in parallel order. 



The branchial sac (PI. XVI, fig. 3, and PI. XVIII, 

 fig. 10) is minutely plicated, the plicae being deeper 

 than usual, and the meshes of the secondary vessels are 

 rather large. The primary vessels vary in size and 

 have a wide membrane along their sides, overlying 

 the undulations on the inner surface, so that a slight 

 longitudinal contraction of the respiratory web would 

 bring their margins together and prevent or regulate 

 the egress of the water contained in the branchial sac. 

 There are eleven or twelve well-developed tentacular 

 filaments, mostly with one or two smaller ones between 



