ISOPODA. 31 



Sphaeroma, Bosc. 



1802, Sphaeroina, Bosc, 'Hist. Nat. des Crustacds,' vol. 2, p. 182. 

 1873, Sphaeroma, Harger, 'Amer. Jouin. Sci.,' ser. 3, vol. 5, p. 314. 

 1880, Sphaeroma, Harger, 'Eep. U.S. Fish. Comm. for 1878,' p. 368. 



1900, Sphaeroma (sensu restrido), Stebbing, 'Proc. Zool. Soc. London,' p. 552. 



1901, Sphaeroma, Stebbing, in 'Spolia Zeylanica,' vol. 2, pt. 5, p. 15. 



1901, Sphaeroma, Stebbing, in Gardiner's 'Fauna, Maldive and Laccadive Arehip.,' vol. 2, pt. 3, p. 710. 



The definition of the restricted genus may he formulated as follows : Sexual 

 dimorphism not conspicuous. Telsonic segment without apical sinus. Maxillipeds 

 having the fourth and fifth joints fringed on the inner margin with long setae, hut 

 neither these two joints nor the sixth produced into lobes. First and second 

 gnathopods having the third and fourth joints fringed on the front margin with long 

 setse. Uropods with subequal rami. 



Conforming to these characters are the type species, S. serratum (Fabricius), 

 S. terebrans, Bate, S. quadridei datum, Say, and S. walkeri, n. sp. In the multi- 

 tude of species which from early dates down to the last two or three years have been 

 assigned to Sphceroma, there are many which are obviously excluded from that genus 

 as above defined. But there are several of which not enough is known to enable 

 us to say whether they belong to it or not. There is a presumption in favour of 

 S. quoianum, Milne-Edwards, since Heller in re-describing that species says that 

 the first three pairs of feet have the middle joints fringed on the outer side with long 

 hairs, and there is a similar presumption in regard to S. sieboldii, Dolleus, 1889, 

 and S. pentodon, H. Richardson, 1904. On the other hand, Whitelegge, describing 

 S. australe, S. latifrons, and S. phimosum in 1902, speaks of the lobes in the palp 

 of the maxillipeds as well developed. At least the first of these three may be referred 

 with some certainty to Exosplmroma. 



Sphaeroma walkeri, n. sp. Plate VII. 



Head not very broad or long. Peraeon convex, its segments not greatly differing 

 in length, although a contrary impression may be produced by the telescoping or 

 extension of a particular segment. The unsutured side-plates of the first segment 

 are as usual much the longest, being subacutely outdrawn backwards and forwards. 

 The next two pairs are apically narrowed, the following three somewhat squared, and 

 the seventh pair with a rather deep trituberculate hind margin. The transverse 

 tuberculatum of the segments, which is scarcely perceptible on the first segment, 

 gradually increases in prominence, and fringes the seventh segment in a very 

 pronounced manner. In the front division of the pleon, representing five faintly 

 distinguishable segments consolidated into one, there is a curved transverse row of 

 tubercles, belonging chiefly to the fourth segment. The telsonic segment is only 

 moderately convex, and becomes slightly concave near the broadly rounded, slightly 



