TUNICATA OF THE PRIBILOF ISLANDS. 



527 



Vas deferens filled with sperm in the specimens at hand, conseijuently large and 

 conspicuous; passes to the left of the intestinal loop. No embryos seen. 



The simplicity of the systems of zooids, the two-lobed atrial languet, and the few 

 i-emote furrows in the wall of the stomach are the most distinctive characters of this 

 species. In the first-mentioned particular it agrees more nearly with A. nordmani, 

 Milne-Edwards, than with any other species of the genus. 



So far as T have been able to ascertain, this is the only instance in the genus in 

 which the atrial languet is two lobed, it being in all other species either one or three 

 lobed. 



A collection contains a half dozen colonies, all from St. Paul Island. 



Amaroucium snodgrassi, uew species. 



General character of the colony. — Form quite variable, but always depressed and 

 cake-like. Area of attachment considerably smaller than the superior free surface. 

 Greatest transverse diameter of largest colony 7 cm., greatest width 5 cm., greatest 

 thickness 2.8 cm. Rather soft and yielding to the touch. Light gray in color, excej)!- 

 ing where covered with sand, which is quite abundant on some of the colonies. The 

 zooids, indistinctly seen on the 

 top surface of the colonies, but dis- 

 tinctly visible on the edges, where 

 the outermost ones show through- 

 out their entire length, as they 

 reach entirely through the thick- 

 ness of the colony. (Fig. 22.) 



Test. — Not in great quantity, 

 there being no central core into 

 which the zooids do not enter. A 

 few sand grains scattered through 

 entire mass. Cells very numerous, 

 but no vessels or fi^bers present. 



Zooids. — Large, each reaching 

 entirely through the thickness of 



the colony; quite straight, and idaced nearly at a right angle to the surface of the 

 colony. As seen on a cut surface of a vertical section of the colony, the thoracic- 

 abdominal portion distinctly set off from the post-abdominal portion by the greater 

 thickness of the former and the lighter but more opaque color of the latter. Post- 

 abdomen joined to the abdomen by a very long, slender peduncle. Total length of 

 zooid from 2 cm. to 2.5 cm.; of this about 4 or 5 mm. are thorax, about an equal part 

 abdomen, and the remainder — 12 or 15 mm. — post abdomen. Systems not readily seen 

 either on surface of colony or on horizontal sections of same; dissection discovers 

 them to be j)resent, however, with about 8 or 10 zooids in each. 



Mantle. — Musculature not highly developed. Longitudinal libers, as UvSual, in 

 bands; circular fibers present, but confined to anterior half of thorax. 



Branchial apparatus. — Branchial orifices found with difficulty on surface of colony; 

 common atrial openings (^uite large, though collapsed and not obvious until searched 

 after. Branchial siphon with six wide, well-defined, though not prominent, lobes. 

 Atrial languet three lobed, at least usually, broad and never very long. Anterior end 

 of thorax usually considerably contracted, so that the various contained organs are 



