IDOTEA PARALLELA. 393 



agree entirely with Costa's description and figure of 

 Id. chelipes in form and structure, as well as with another 

 specimen in the same collection labelled by Signor Costa 

 himself. 



It is evident, however, that the C. chelipes of Fabricius 

 and Latreille cannot be identified with the animal before 

 us, the ** Cauda'^ tridentata of the Fabrician description 

 being entirely distinct from the remarkable character of 

 the extremity of the tail of /. parallela. Signor Costa 

 states of his species, " Trovasi ne' mari d'Inghilterra e di 

 Zelandia," taking the habitat from Pallas by regarding 

 his species as the Oniscus linearis of Pallas' " Spic. ZooL' 

 fasc. 9, t. 4, f. 17 and 18. These figures are indeed bad, 

 but there can be little doubt that they represent small 

 and narrow specimens of /. tricuspidata, and we believe 

 Fabricius was correct in referring Pallas' figures to his 

 C. chelipes, as Pallas describes the tail of his species as 

 obscurely tridentate, and indeed refers his linearis to 

 O. chelipes of his former work, from which probably Fabri- 

 cius had taken it up. 



