BE. W. A, HEEDMAN" Otf BEITISH TTTFICATA. 283 



(PL XVI. fig. 2). Alder states that it is smooth, and Kupffer 

 and Traustedt mention the ribs, but refer to the edge as smooth. 

 The tentacles (PI. XVI. fig. 3), which in my specimens are small 

 and slender, rather distantly placed, 32 in number, and of three 

 sizes alternating (eight large-, eight medium-, and sixteen small- 

 sized), are described by Alder in A. pustulosa as few and stout, 

 while Kupffer and Traustedt say that they number fifty or more ; 

 their relative size and arrangement is not referred to in any of 

 the descriptions. 



Ascidia tkiangttlaeis, n. sp. (Plate XVI. figs. 4-7.) 



External appearance. — Shape triangular, not compressed ; an- 

 terior end narrow, forming a rounded point ; posterior end wide, 

 straight, elongated dorso-ventrally ; ventral edge almost straight, 

 dorsal sloping backwards to join the rounded dorsal edge of the 

 posterior end. Attached by the entire extent of the posterior 

 end, and the ventral half of the posterior end of the right side. 

 Branchial aperture terminal, sessile ; lobes regular and distinct, 

 but not projecting ; atrial aperture on dorsal edge, one third of 

 the way down, slightly projecting, directed dorsally and poste- 

 riorly. Surface prickly, covered with minute pointed projections 

 all over, except on the centre of the left side, and at the anterior 

 end round the branchial aperture. Colour light grey ; when 

 living the apertures were slightly pink. Length 2*3 centims., 

 breadth (at posterior end) 2 centims. 



Test rather thin and soft, but moderately strong, transparent. 

 Course of intestine seen through distinctly from left side. 



Mantle delicate, adhering slightly to inner surface of test; 

 musculature distinct but fine. 



Branchial sac a little irregular, but not longitudinally plicated. 

 The alternate transverse vessels wider than the intermediate ones. 

 Internal longitudinal bars distinct and strong, borne on long 

 ducts ; no papillae. Meshes almost square, containing each about 

 six stigmata. 



Dorsal lamina transversely ribbed ; margin minutely denticu- 

 lated, three or four denticulations between each pair of ribs. 



Tentacles rather small and distant, 15 larger, and nearly the 

 same number of small intermediate ones; in some spaces the 

 intermediate one is absent. 



Olfactory tubercle irregularly lozenge-shaped, opening ante- 

 rior; horns bent in, but not coiled. 



