50 U.S. NATIONAL MUSEUM BULLETIN 291 



Morphometry. — Although relatively few specimens of B. hacidifera 

 are available, they represent a broad range of sizes from larvae of 

 6 mm to fully ripe adults of 37 mm mantle length. Standard measure- 

 ments have been made to determine the gross features of growth of 

 B. hacidifera and to compare these features with B. abyssicola. The 

 morphometric values are plotted as pluses ( + ) on the scattergrams 

 for B. abyssicola (figs. 1 to 13) ; this allows a direct comparison of the 

 morphometric characteristics of the two species. In B. hacidifera^ as in 

 B. abyssicola^ the data indicate that the growth of the body parts that 

 were analyzed is allometric with respect to mantle length. 



Discussion. — The Dana and Eltani-n material used in this work 

 show that B. abyssicola and B. hacidifera are sympatric in the tropical 

 eastern Pacific Ocean. Certain statements in the literature indicate that 

 the two species may also be sympatric in the equatorial waters of the 

 Indian Ocean. Reports of specimens from these two areas may refer 

 to either species or both. In most instances, however, it is difficult to 

 determine the identity of the material. 



Chun (1910) had five specimens of Bathyteuthis taken by the Val- 

 divia ; four were captured in the Indian Ocean Equatorial Water Mass. 

 The specimens ranged from 9-18 mm mantle length. In a separate sec- 

 tion on the details of arm structure, Chun noted that the largest speci- 

 men lacked the protective membrane between the strong muscle sup- 

 ports (trabeculae) and that the trabeculae looked like cirri. All smaller 

 specimens had well-developed protective membranes. Therefore, 

 Chun's largest specimen probably represents B. hacidifera^ while the 

 remainder of the specimens probably refers to B. abyssicola. Unfortu- 

 nately, it is impossible to be sure to which species Chun's description 

 refers except in sections where he mentions particular specimens. 

 Since the largest specimen is only 18 fnm in mantle length, probably 

 most of the description applies to it, especially the descriptions of the 

 eye and internal structures. 



Pfeffer (1912) had three larval specimens that he considered to be 

 Bathyteuthis {Benthoteuthis) . The specimen from the Mediterranean 

 was a larva of Ctenopteryx (see Historical Resume). The two remain- 

 ing specimens were from widely separated localities in the Atlantic. 

 Since the two larvae were only 3 and 4.5 mm mantle length, it seems 

 unlikely that Pfeffer could have derived his detailed description from 

 them. For the greater part, it appears that Pfeffer's information is 

 based on Chun's description. Pfeffer's specimens from the Plankton 

 Expedition were undoubtedly B. abyssicola., but since most of his de- 

 scription is based on Chun's work, it necessarily includes a mixture of 

 both species. Pfeffer stated that the protective membranes of lai'val 

 specimens disappear in older specimens and that only the cross-struts 



