TUNIC ATA OF THE PRIBILOF ISLANDS. 521 



Digestive tract. — Oesophagus rather wide at its mouth, issuing from nearly the mid- 

 dle of the posterior end of the branchial sac, distinctly curved so as to enter the stomach 

 on its right dorsal side. Stomach globular, smooth walled. Intestinal loop rather 

 wide, slightly shorter than the combined length of oesophagus and stomach. Two well- 

 marked constrictions in the intestine at the base of the loop, these including between 

 them the base of the U-shaped loop; the rectum passing to the left of the cesophagus 

 to reach the atrial chamber. Anus sometimes with a wide, flaring lip. (Fig. 18.) 



^exual organs. — Ovary not large, situated far back in the post-abdomen, behind 

 the testis. The entire post abdomen so filled with mesenchymatous cells that the 

 sexual organs are mucli obscured; no distinct lobulation of either ovary or testes 

 observable. The embryos, developing in the atrial chamber, greatly distend and dis- 

 tort this cavity. 



This species appears to be more closely related to P. aurantium, Milne-Edwards, 

 than to any other member of the genus. The last named species is, however, described 

 by both Milne- Ed wards, 1842, and Lahille, 1890, as having a gelatinous test, and no 

 mention is made by either of these authors of the network of fibers in the test. This 

 latter character, I take it, constitutes a distinct difference between the two. The 

 presence of such a network seems to be of such 

 rare occurrence in Polyclinum that were it pres- 

 ent in P. aurantium, Lahille, whose studies were 

 largely morphological, would have noted it. 

 . Furthermore, according to the figure of a zooid 

 of P. aurantium, given by Mihie-Bdwards (PI. 

 Ill, fig. 4, h), the postabdomen of this species is 

 relatively much longer than in T. pannosum. 



There are about two dozen colonies of this 

 species in the collection, all from St. Paul Island. 



Aplidiopsis jordani, new species. 



General character of the colony. — Massive, ~~ Tus. 



irregularly polyhedral in form, the three dimen- B 



sions not greatly different. Attached by a small 



area only (fig. 19). Quite hard and unyielding to the touch; surface rather uneven. 

 Light gray in color, with the yellowish zooids distinctly visible. A thin surface 

 layer of test considerably harder and less transparent than the interior portions, 

 which latter is (luite transparent. A few sand grains imbedded on the surface. 



Greatest diameter of the one colony in the collection, 2.3 cm.; least diameter, 

 1.5 mm. 



Cells in test very numerous, rather uniform in size. No vessels present in the test. 



Zooids. — Eather large and numerous, readily seen on the surface of the colony. 

 No systems present, each zooid opening to the surface by its own atrial orifice. Many 

 of the individuals placed at very oblique but differing angles to the surface of the 

 colony, so that they are crossed by and wound around one another. Post-abdomen 

 not pedunculated. A finger-like ectodermal process projecting from posterior end of 

 body. Total length about 8 mm., one-fourth of which is branchial sac, another fourth 

 intestinal loop, and the other half post abdomen. (The post-abdomen outlined in fig. 

 L'O is unusually short.) Post-abdomen very large at its posterior end, and is dense and 



