350 THE REV. T. R. R. STEBBING ON 



ISOPODA GENUINA. 

 Tribe FLABELLIFEIIA. 



Fam. Sph^romid^. 



1847. Sj)/aero)i(idce White, List of Crustacea in 13rit. IMiis., 



p. 102. 

 1910. „ Stebbing, Ann. S. Afr. Mus. vol. vi. p. 42G. 



Gen. Exosni.EROMA Stebbing. 



1900. Exotij^Jntroma Stebbing, Pr. Zool. Soc. London, p. 55,'5. 

 1905. ,, Hansen, Quart. J. Microsc. Sci. vol. xlix. 



pp.103, 118. 

 1910. ,, Stebbing, Ann. S. Afr. Mus. vol. vi. p. 428. 



This genus is placed by Hansen in the section Sphseromini of 

 his group SphseroniinsB hemibrancbiatse, 



ExoSniyEROMA CALCAEEUS (Dana). (PI. 11.) 



1853-55. Sjiherotaa calcarea Dana, U.S. Expl. Exp. vol. xiii. 



p. 776, pi. 52, Hg. 2 a-c. 

 1891. Sjihceroma „ Dollfus, Miss, du Cap Horn, Crust. 



p. 64, pi. 8 a. figs. 7, 7 a, 7 l>. 

 1913. Exosphce7-oma coatsii Tattersall, Tr. R. Soc. Edinb. vol. xlix. 

 p. 885, figs. 3, 4. 

 This is one of the species which are now in rapidly increas- 

 ing number perplexing the sj'stematist by their variability. A 

 comparison of the figure supplied by iJana in 1855 with 

 Dr. Tattersall's in 1913 would scarcely suggest a suspicion of 

 specific identity. As it is, probably some allowance must be 

 made for a little want of detail in Dana's sketch. But Dollfus, 

 who had at command several specimens, explains that the 

 granules and tubercles on the general surface and the double 

 crest on the pleon sometimes disappear, leaving a smooth form 

 such as Dana represents. Dr. Tattersall, describing and figuiing 

 an adult female and a young form, from Dr. Bruce's Scottish 

 Antarctic Expedition, noted the comparative infrequency of 

 tubercles in the young, with other differences, but he had no 

 mature male to test for sexual difference. This deficiency I have 

 been able to supply from Mr. Vallentin's collections. The 

 specimen figured was 13 mm. long by 7 mm. broad. A female, 

 16 mm. long, containing a great number of eggs, was taken by 

 Mr. Vallentin at low ebb of a spring tide in Stanley Harbour, 

 Nov. 12, 1901. Other specimens, taken at Rapid Point, low 

 water, Jan. 30, 1911, comprise a male 19 mm. long by 10 mm. 

 broad at the sixth per;eon segment. This capture corroboiutes 

 the statement by Dollfus that he had observed males which were 

 strongly granular and othei-s almost smooth. Variation also 

 affects the colour, at least to judge by j^reserved specimens, 

 [10] 



