Species o/'Amjjhithoe. 113 



care the force required to draw tliem out ends by breaking 

 them off. The whole creature is comparatively hard, and 

 readier to break than to bend. 



In the first two pairs of pereiopods the thigh is largely deve- 

 loped. Of the three following pairs the first is short and the 

 last long, the second being intermediate in size. 



The telson, which, with the preceding segment, is sulcate, 

 is almost buried between the last pair of pleopoda ; these 

 converge at their distal ends, each bearing a pair of sharp 

 hooks with their points facing outwards. 



The length is one fifth of an incli nearly. 



Amjyhithoe ruhricata. PI. XI. figs. 2, 2 a. 



This is not an uncommon species, found occasionally within 

 tide-marks, but generally rather further out. The principal 

 distinction from its first cousin,^. ZtYtorena, which is generally 

 a pure green speckled with black, consists in its bi'ight red 

 colouring, sometimes varied by a white pattern along the cen- 

 tral line of the back. Colour, however, and habitat are in 

 general so little to be depended on for discriminating species, 

 that it seems, in the present instance, worth while to point out 

 how minute all the other differences are between A. ruhricata 

 and A. littorina. The former appears pretty constantly to 

 have the flagellum of the upper antennas slenderer and of 

 greater comparative length. Its eyes are said by Mr. Spence 

 Bate to be white with black spots, whilst those of its congener 

 are described as black. According to my own experience they 

 are red in both cases. In the ' British Sessile-eyed Crustacea' 

 the hands of the first and second gnathopods of ^. mhricata 

 are described as "having a slightly defined palm;" but in 

 Mr. Spence Bate's British-Museum Catalogue the palm is said 

 to be " not defined." In the former work the second gnatho- 

 pods oi A. littorina are said to have the palm " long and not 

 clearly defined." We are also there told that " there is a deep 

 semilunar fissure between the wrist and the hand and between 

 the wrist and the preceding joint, which does not occur in 

 A. ruhricata^ Of this nothing is said in the Catalogue, in 

 which, indeed, the gnathopods of the two species are described 

 in terms almost identical. The truth seems to be that the 

 palm of the second gnathopods is subject in both forms to a 

 certain amount of variation, its tendency being towards a well- 

 defined concavity in the deep-water form. In this form also 

 the fingers of both gnathopods have a well-defined serration, 

 and that in adult as well as in young specimens. But this 

 serration occurs certainly also in the finger of the first gnatho- 

 Ann. (& Mag. Nat. Hist. Scr. 4. Vol xiv. 8 



