MUSEUM OF COMPARATIVE ZOOLOGY. 185 



No. 7. — Interim Report of the Hydroids collected by L. F. de 

 Pourtales during the Gulf Stream Exploration of the United 

 Slates Coast Survey. By George T. Allman. 



(Published by permission of Prof. B. Peirce, Supt. U. S. Coast Survey.) 



Setting 'aside a very few whose imperfect state of preservation ren- 

 dered their determination impossible, the whole of the specimens forming 

 the collection may be distributed among seventy-three species. Of these 

 species sixty-three are undescribed, two have been already described by 

 M. de Pourtales, and, like the undescribed species, have not yet been ob- 

 tained beyond the area of the Exploration ; while the remaining eight, so 

 far as the diagnosis of specimens in almost every casedestitute of gonosome 

 can be relied on, occur also on the eastern side of the Atlantic. It 

 must be borne in mind, however, that the identification of specimens in 

 which the gonosome is wanting cannot be regarded as absolute. 



Eleven species belong to Gjmnoblastic genera. Of these one has 

 been already described by M. de Pourtales. Of the remaining ten, 

 seven have their hydranths sufficiently well preserved for description ; 

 while the remaining three, retaining nothing but the tubular perisarc with 

 at most the included coenosarc, can be referred only provisionally to 

 definite species or even to definite genera. 



Only one of the Gymnoblastic Hydroids admits of being referred 

 with any degree of probability to a species occurring on the eastern 

 shores of the Atlantic. This is a large, simple-stemmed form, which 

 cannot be distinguished from Tubularia indivisa ; but as nothing re- 

 mains of it beyond the stems, it would be rash to assert positively that 

 it is identical with the Tubularia indivisa of the European shores. 



Of the Calyptoblastic form-; there are sixty-two species in all. Of 

 these fifteen belong to the Campanularinaj, while forty-seven must be 

 referred to the Sertularinaj. 



Of the fifteen species referable to the Campanularinse one has been 

 already described by M. de Pourtales, while- two others cannot be dis- 

 tinguished from the Filellum immersum and the Halecium muricatum of 

 the European shores. In the absence of hydranths and gonosome, 



