A TAXONOMIC STUDY ON PYROSOMA — METCALF AND HOPKINS. 251 



D. 5403, Capitancillo Island Light, off northern Cebu Island; March 

 16, 1909; 182 fathoms; surface temperature, 81° F.; two specimens, 

 Cat. No. 6410, U.S.N.M. 



D. 5408, Capitancillo Island Light, off northern Cebu Island; March 

 IS, 1908; 159 fathoms; surface temperature, 80° F.; surface den- 

 sity, 1.02462; five specimens, Cat. No. 6440, U.S.N.M. 



One specimen, from Ward's Natural Science Establishment, from 

 the "South Pacific," Cat. No. 3182, U.S.N.M. 



Six specimens from the Southern Californian coast, 1 mile south 

 of Catalina Island, U.S.N.M., "ace. 397, T. 127. 3-30-16." 



One hybrid of Pyrosoma atlanticum dipleurosomaxP. atlanticum 

 paradoxum. 



D. 5196, Capitancillo Island, off northern Cebu Island, Philippine 

 Islands; April 3, 1908; surface; surface temperature, 82° F.; surface 

 density, 1.02518; one specimen, Cat. No. 6420, U.S.N.M. 



PYROSOMA ATLANTICUM, subspecies GIGANTEUM (P. GIGANTEUM, Lesuenr, 1815). 



Plate 30, fig. 37. 



This is the best-known form of Pyrosoma, as it was one of 

 the first to be described and occurs in relative abundance in the 

 North Atlantic Ocean. But in the several attempts to work out 

 its distribution there has been great confusion and misunderstanding. 

 As P. atlanticum, giganteum we recognize a form which reaches its 

 typical development in the Atlantic Ocean — a Pyrosoma which 

 ordinarily attains a large size and is recognized by certain character- 

 istics which, if taken together, make it rather distinct. It seems to 

 intercross, however, with other less specialized races of the major 

 species atlanticum, so that its identification is not at all certain 

 unless typical specimens are at hand. Consequently, if we are to 

 continue the use of this name giganteum it ought to designate a par- 

 ticular, well-defined subspecies or variety. The application of this 

 name to all Pyrosomas of large size leads to misunderstanding as to 

 the identity of the one in question; for size alone, unless shown 

 through extensive collections to be distinctive, is at best a poor 

 criterion by which to identify a Pyrosoma. 



We have 16 Pyrosoma colonies, from 15 different stations in the 

 Atlantic Ocean, which truly correspond to the published descrip- 

 tions of "P. giganteum." Fully 13 other Pyrosomas were collected in 

 the same waters, from 1 1 stations, which might very well be referred 

 to the same subspecies. We have chosen, however, to treat these 

 latter apart from the more typical 16, not because we believe they 

 are a distinct race, but in order to avoid confusion in describing 

 the subspecific character. As mentioned above in connection with 

 P. atlanticum atlanticum, it is possible that these various aberrant 

 specimens found in the Atlantic result from the intercrossing, perhaps 



