26 ASCIDIIDiE. 



Ascidia callosa. 



Plate XXIII. Fig. 318. 



Ascidia callosa, Stimpson, Proc. Bost. Soc. N. II. iv. 228 (1852) ; Check Lists, 2 (1860). 

 — Packard, Invert, of Labrador, in Mem. Bost. Soc. i, 276 (1867). 



Body depressed, usually oval or oblong, but varying in shape. 

 Tost, when free from the parasitic growth which usually covers it, 

 of a light sepia or pale bluish color, translucent, although thick 

 and fleshy. Its thickness varies in different parts of the body from 

 the character of the surface, which is very rugose, rising into 

 irregular prominences and ridges. Apertures dark purple or red- 

 dish, situated on prominent warts ; the seven-rayed branchial, 

 which is largest, being terminal, and the six-rayed anal removed 

 from it by a distance less than one half the length of the body. 

 The branchial tube within has seven strong longitudinal ridges. 

 Branchial sac finely reticulated. The inner tunic, where it covers 

 the abdomen, is marked with crowded golden specks. Length, 

 often three inches ; breadth, two inches. This species is abundant 

 in Passamaquoddy Bay, from low-water mark to thirty feet. It is 

 usually found adhering broadly by the left side to the under sur- 

 face of large stones. (^Sllmpson.~) 



Grand Manan (^Stimpson); Strs. of Belle Isle, Packard, one of 

 whose specimens, preserved in alcohol, is drawn on Plate XXIII. 



Genus CIIELYOSOMA, Broderip and Sowerdy. 1830. 



Body depressed, oblong, fixed, sessile; test coriaceous, its up- 

 per surface consisting of eight somewhat horny, angular plates; 

 orifices small, prominent, perforating the plaited surface, each sur- 

 rounded by six triangular valves ; gills plicated ; tentacles simple. 



Chelyosoma geometriciim. 



Ascidia (jpometrica, Stimpson, Proc. Bost. Soc. N. II. iv. 229 (1852). 

 Chelyosoma rjcometrica, Stimpson, Smith. Inst. Check Lists, 1 (1860). 



Body adhering by a broad base, depressed, oval. Test thin, 

 smooth, transparent, very pale greenish, with an almost peripheric, 

 narrow, dark-colored line or ridge, like a fibre, from which other 

 lines of the same character proceed, dividing the surface into ten 

 irregular polygons, two of which, separated from each other by a 



