1894.] NATURAL, SCIENCES OF PHIEADELPHIA, 191 



A NEW SPECIES OF THE ISOPOD-GENUS BATHYNOMUS. 

 BY DR. A. ORTMANN. 



Ill the year 1877, A. Agassiz dredged at 955 fathoms, in the Gulf 

 of Mexico, a gigantic Isopod, described by A. Milne-Edwards 

 (Conipt. Rend. Acad. Sc, t. 88, 1879, p. 21, and Annal. Magaz. 

 Nat. Hist. (5) III., 1879, p. 241) as Bathynomus giganteus. De- 

 lineations of this form were subsequently published by Filhol (La- 

 vie au fond des Mers, Paris, 1885, p. 147), ^ and by A. Agassiz (Three 

 Cruises of the "Blake." Bull. Mus. Compar. Zool., Vol. XV., 1888, 

 fig. 252. ) Wood-Mason and Alcock made mention of the same species 

 (Annal. Magaz. Nat. Hist. (6) VII., 1891, p. 270) taken by the 

 "Investigator" in the Bay of Bengal at 740 fathoms. Lastly, 

 Hansen (Det K. Dansk. Vidensk. Selsk. Skr. Nat. Math. Afd. (6), 

 V. 3, 1890, pp. 252, 318, 378) pointed out the close resemblance to 

 the family Cirolanida^ while Milne- Edwards proposed to place this 

 genus in a new group or family, " Cymothoadiens branchifhres." This 

 latter opinion was adopted by Wood- Mason and Alcock in creating 

 the family Bathynomidie. 



After a careful examination of both opinions I believe Hansen's 

 classification to be correct. 



Bathynomus giganteus, which is remarkable, not only for its enor- 

 mous size, but also for other morphological characters, was hitherto 

 the only species of the genus. I describe herein a second species 

 collected by L. Doderlein, during his sojourn in Tokio, Japan (1880- 

 81), which, although smaller than the other, always attains dimen- 

 sions unusual among the Isopoda. I propose to name the new species 

 in honor of the discoverer, Bathynomus ddderleini. 



Diagnosis. — Body more slender than in B. giganteus, three times 

 as long as broad (B. giganteus is not two-and-a-half times as long 

 as broad). The last segment of the body (telson) is but little 

 broader than long, its posterior margin is provided with seven spines, 

 the middle one of which is the greatest. In the median line of the 

 upper surface is a distinct longitudinal ridge. Both branches of the 

 uropoda are pointed at the ends. 



1 I have only seen the copy in Marshall, Die Tiefsee und ihr Leben, 1888, p. 261, 

 fig. 86. 



