REPORT ON THE TUNICATA. 177 



Polycarpa longisiphonica, Herdman (PL XXIII. figs. 3-G). 



Polycarpa longisiphonica, Herdman, Prelim. Rep., J'roc. Roy. Soc. EJin., 1880-81, p. 77. 



External Appearance. — The body is oblong, or somewhat flask-shaped, and erect. 

 The posterior end is large and rounded, the anterior end narrow and pointed. It is 

 apparently not attached, or only slightly by the posterior third of the left side. The 

 apertures are conspicuous, at the ends of very long siphons; the branchial is terminal, 

 and is directed anteriorly ; the atrial is on the dorsal edge, half way down, and is directed 

 dorsally and anteriorly ; it is fully as long as the branchial siphon. 



The surface is covered, except on the siphons, by a fine coating of sand and shell 

 fragments. The colour is a dark brown. 



Length of the body, 7 cm. ; breadth of the body, 4 cm. 



The Test is thin and brittle, but rather stiff. 



The Mantle is thin, and adheres closely to the test. The musculature is feeble. 



The Branchial Sac has four folds upon each side. Every fifth or sixth transverse vessel 

 is wider than the intermediate ones, which are all of one size. There are eight internal 

 longitudinal bars on the folds, and about the same number in the interspaces. The 

 meshes are square, they contain each four to six stigmata, and are occasionally divided by 

 a narrow horizontal membrane. 



TJie Dorsal Lamina is a narrow and plain-edged membrane. 



The Tentacles are not very long, and are placed rather far apart. There are about 

 eighteen, some shorter than others, but not placed symmetrically. 



The Dorsal Tubercle is circular iu outline, or somewhat horse-shoe- shaped, with both 

 ends turned slightly outwards. 



This species resembles Polycarpa rigida in its erect body and stiff test, partly covered 

 with adhering foreign matter (PI. XXIII. fig. 3). If attached at all, it is only slightly 

 so by the posterior part of the left side. The length of the siphons upon which the aper- 

 tures are placed is a characteristic feature. 



As in the last species, the transverse vessels are of two sizes (PI. XXIII. fig. 4, tr. and 

 tr.'), but here the internal longitudinal bars are narrow, and not wide as in Polycarpa 

 rigida. The interspaces are wide, and have each about eight rows of meshes. The 

 internal longitudinal bars are crowded on the folds. In one of the specimens of this 

 species all the vessels in the sac appear to be rather wider. The ordinary meshes in 

 the interspaces are square, or a little elongated transversely, and are occasionally divided 

 by narrow horizontal membranes. 



The tentacles are of different sizes, but these are not arranged symmetrically. In one 

 specimen examined there were about sixteen larger tentacles and two or three very small 

 ones between each pair of larger. There is a double line of columnar cells (probably 

 ciliated when Hving) running down the anterior face of each tentacle, and becoming 



