Mr. F. S. Conant on the Chcetognaths. 211 



IV. Systematic. 

 The known Chcetognaths of American Waters. 



1 . Sagitta elegans ( Verrill) . 



Strodtmann mentions this species {he. cit.)^ but was unable 

 to find a description of it in the literature at his command. 

 Professor Verrill's account is found on page 332 [626] of the 



* Eeport upon the Invertebrate Animals of Vineyard Sound 

 and Adjacent Waters ' (Washington, Government Printing 

 Office, 1874). 



S. elegans resembles the widespread 8. hipunctata. The 

 length of the largest specimens in my possession is 2.5-30 

 millim. Maximum breadth 1 millim. Caudal segment one 

 fifth total length. Fins 5, like those of hipunctata or hispida. 

 Seizing-hooks 9-12, shaped as in hipunctata. Anterior teeth 

 5-7. Posterior teeth 12-15. Corona ciliata elongated, 

 sinuous, oval, as in hipunctata or hispida. Diverticula of 

 intestine both external and internal, as described in the pre- 

 ceding. Accessory longitudinal septa present in caudal 

 segment. Tactile prominences generally few as compared 

 with 8. hispida (see fig. 7 in 'Circular' for June 1895). 

 Musculature of body not so stoutly developed as in hispida. 

 Head well marked off from trunk. Epidermis thickened 

 around the neck. 



8. elegans differs from hipunctata in size, in the relative 

 proportions of caudal and body-segments, and in the presence 

 of diverticula from the intestine. It is found at Wood's Holl, 

 Mass., in winter, sometimes in great abundance. In summer 

 it is rare there. None of the many specimens that I have 

 seen, taken in the winter months by Mr. Vinal Edwards, of 

 the Fish Commission, contained mature ova. 



The name elegans was applied by Professor Verrill to 

 specimens 16 millim. long ; he also mentions a " much larger 

 and stouter species than the preceding, taken in abundance in 

 Vineyard Sound from Jaimary to May, 25-30 millim. long." 

 I have not been able to find any specific difference between 

 the large and small specimens from Wood's Holl, and do not 

 doubt that they are the same. 



Strodtmann mentions a " 8. gracilis,''^ figured by Verrill 

 in the " Results of the Explorations made by the Steamer 



* Albatross ' off the Northern Coast of the United States in 

 1883." Professor Verrill has very kindly replied to my 

 inquiry in reference to this, that the figure is of 8. elegans, 

 the name " gracilis " being the result of a clerical error. The 



