292 A. E. Verrill on Ascidians from New England. 



The individual zooids are elongated and slender ; the post- 

 abdomen more slender, usually considerably exceeding in 

 length the rest of the body, and but slightly constricted at 

 base ; the thorax and abdomen are shorter and stouter than in 

 the preceding species ; branchial sac with about 12 transverse 

 vessels; stomach oblong-oval, with numerous longitudinal 

 glandular folds ; intestine large. Branchial orifice with six 

 short lobes ; anal orifice terminal or nearly so, close to the bran- 

 chial, with an acute upper lobe. 



Color, in alcohol, milky white, subtranslucent ; zooids yel- 

 lowish. One of the larger zooids measured -31 of an inch in 

 length ; the thorax -085 ; the abdomen -062 ; the post-abdomen 

 •165 ; diameter of thorax '045 ; of post-abdomen -025. 

 Wood's Hole, Mass.,— Prof H. E. Webster. 

 This species is easily distinguished from all the preceding bj 

 its large, upright fronds, circular systems, and the regular stellate 

 arrangement of the zooids, and by its firmer texture and smooth 

 surface. 



MacrocUnum, gen. nov. 

 Allied to Aplidium, forming thick, fleshy masses, of various 

 forms ; without cloacal openings or common ducts, each indi- 

 vidual having its own branchial and anal orifices, side by side. 

 Systems scattered, usually rather indistinct. Animals elongated, 

 slender; post-abdomen narrow, much longer than the abdomen 

 and thorax taken together, filled with voluminous ovaries, 

 placed on each side of the median duct ; eggs small and very 

 numerous ; stomach deeply lobed ; intestine long, often convo- 

 luted ; anal orifice terminal or subterminal, near the branchial, 

 subcircular or somewhat bilabiate, the upper side with a rather 

 prominent lobe ; branchial with six rounded lobes or short pa- 

 pillae. Type, M. crater. „ , 

 Savigny included in his genus Aplidmm two "tribes, eacti 

 containing several species, but differing considerably m struc- 

 ture. In the first tribe, to which the name, ApUdum, should oe 

 restricted, the post-abdomen i 

 short and rounded and tbe 

 ovaries are clustered and coD- 

 I tain few large ovules; thean'U 

 ^ orifice is on the side of J 

 thorax and distant from JJ 

 branchial. The seco^<i^*"S 

 appears to correspond neaxiy 

 with our genus, MacrocUnum, the post-abdomen being 

 long, with the ( • '^ ^ i . .._.wth. 

 considerable <' 



enus, MacrocUnum, the post-abdomen wiug ,^ 

 he ovaries arranged along each side ; hvd t _ ,^ 

 3 diversity in the arrangement of the anal onnct;.. 



... ......... :„„.i,rnn^h the middle, 



