THE ASCIDIANS 



241 



form a series, S. greeleyi having the longest peduncle ; ^S". Jiionterey- 

 ensis the next and 6'. yakutatensis the shortest. S. yakutatensis dif- 

 fers from kS. montereye?isis, also in possessing a maximum of less than 

 fifty tentacles ; whereas montereyensis reaches as high as one hundred. 

 The difference between yakutatensis and ntontereyensis in the struc- 

 ture of the sac cannot be regarded as of specific importance. 



In large specimens of greeleyi the first and fourth folds of the sac 

 possess a considerably greater number of bars than they ever appear to 

 have in yakutatensis. Furthermore, the bilobed condition of the anus 

 in greeleyi does not occur in yakutatensis. 



Further study of specimens from localities between those from which 

 these three species come, may be expected to throw light on the 

 relations of this interesting series. The collection contains about 

 seventy specimens of all sizes, all taken from a reef near Khantaak 

 Island, Yakutat Bay, at extreme low tide, on June 21, 1899. 



STYELA TRUNCATA sp. nov. 



(PI. xxvii, figs. 22 and 23.) 

 Ge?ieral characters. — Irregularly cone-shaped, attached by the base, 

 which is cleanly truncated by the surface which serves to attach it ; the 

 base distinctly broader than any other transverse section of the body. 

 Several of the largest individuals inclined somewhat to one side. 



MEASUREMENTS . 



Siphons small and near together ; in larger specimens almost en- 

 tirely hidden by the large irregular tubercles of the test which beset a 

 small area of the anterior end. The remaining portions of the body 

 nearly even and smooth, though in some specimens more or less cov- 

 ered with an encrusting bryozoan. Color of whole anterior end a 

 reddish brown, siphons not differing from surrounding portions. Test 

 rather thin, but firm ; mantle thin, the musculature being rather feebly 

 developed. 



^ The measurements of the smallest one in the table are exceptional ; in general, 

 the proportions of the small specimens more nearly agree with the largest one in 

 the table. 



