/ 276 



Pontoporeia Hoy« Smith, lias, I think , been reported only from 

 Lake Superior and Lake Michigan, and the only American locality for 

 My sis relitta, Loven, has been these same lakes. In fact, a compari- 

 son of this list with those published by Smith and Forbes of the 

 fauna of the Great Lakes shows that the fauna of the deep water of 

 Green Lake is almost identical with that of Lake Michigan. 



Ripon, Wis., Ü. S. A.. May 18, 1S91. 



4. Preliminary Note on the Anatomy and Histology of Serpula dianthus 



(Verrill). 



By Aaron L. Tr eadwell , 

 Biol. Labor. "Wesleyan University, Middletown, Conn., U. S. A. 



eingeg. 2. Juni 1891. 



The following observations were made on specimens collected 

 during July and August, 1890, while at work in the Biological Labo- 

 ratory at Cold Spring Harbor, Long Island. They were preserved by 

 immersion in picric acid for from 15 — 20 minutes, followed by alcohol 

 of the various grades up to 85^, in which they were finally preser- 

 ved. The internal anatomy was studied entirely by means of serial 

 sections, the specimens being too small to admit of gross dissection. 



Serpula dianthus is one of the commonest sedentary annelids of 

 the New England coast, living below low water mark , when its long 

 calcareous tubes may be found attached to stones, oyster shells etc. It 

 was first described by Prof. Verrill 1 . 



There is, however, one slight error in Prof. Verr ill's descrip- 

 tion. He has throughout confounded the dorsal with the ventral side. 

 Thus, the mantle is attached to the ventral, rather than the dorsal, 

 side, and the clumps of large setae are directed upward, rather than 

 downward. Owing to the extraordinary development of the dorsal 

 longitudinal muscles the animal when coiled has its dorsal side con- 

 cave, rather than convex, as in other annelids. This may have led to 

 the error. 



An operculum is always present, attached to the dorsal outer end 

 of the base of the branchiae , on one side of the body. This is some- 

 times developed on the right side, and sometimes on the left. 



Occupying a corresponding position on the opposite side of the 

 body from the operculum, is the small rudimentary pseudoperculum. 

 This is sometimes a mere knob , but in other individuals it undergoes 

 a considerable development. It never attains, however, more than half 



1 U. S. Fish Commission Report. 1872. »Invertebrates of Vineyard Sound « 



