TAGURIDEA LITHODES MAIA 



177 



reduced and carried tightly flexed on to the ventral surface of 

 tlie thorax. They live a free, unprotected existence, and are 

 highly calcified. They are, however, certainly Pagurids, as is 

 evidenced by a number of anatomical characters, but most 

 clearly by the asymmetry of the abdomen, especially in the 

 female, which is not only markedly asymmetrical in the arrange- 

 ment of its dorsal plates (Fig. 121), but also in the presence of 



Fig. 121. — Lithodes maia, 9 , in ventral view, x |. The abdomen is flexed on tlie 

 thorax, so that its dorsal surface is seen. 1.3, Lateral plates of third abdominal 

 segment ; 1.5, left lateral plate of fifth abdominal segment ; m, marginal plate ; T, 

 brush -like last pereiopod ; Te.6, telson and sixth abdominal segment. 



three pleopods upon the left side only, as in Birgus. The male 

 is without these appendages, and the sixth pair of pleopods is 

 absent in both sexes. The remarkable calcified plates upon the 

 abdomen bear a superficial resemblance to those in Birgus, but 

 their evolution is traced, not from a Cenobite, but from an 

 Eupagurine stock.^ 



In some of the Eupagurinae, e.g. Pylopagurus, feebly calcified 

 plates are present upon the segments "of the abdomen 

 (Fig. 122, A). 



In the most primitive of the Lithodidae we witness the 



1 Brandt, Bull. Fhijs. Math. Acad. St. Pitershourg, i. p. 171, and viii. p. 54 ; 

 Boas, K. Dansk. Vidensk. Selskab. Skrift. Naturvid. og Math. Afd. 6, Bd. 2, 1880 ; 

 Bouvier, Ann. Sci. Nat. (Zool.) (7) xviii. p. 157. 



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