590 THE VOYAGE OF H.M.S. CHALLENGES. 



When Milne-Edwards published his Histoire Naturelle des Crustaces in 1837, there 

 were twenty-two species of Hippolyte known, and these he classified under three 

 distinct divisions, dependent upon the extent to which the dorsal carina extends 

 posteriorly. To these Dana added five, arranged in two divisions, corresponding with 

 the first and third divisions of Milne-Edwards, and classified on the same character, 

 and many others have since been added by Stimpson, Heller, Kroyer, Sars, and other 

 carcinologists. To these may be added the specimens in this collection which differ 

 from the typical Hippolyte of Leach in more or less important anatomical features, but 

 all of which have certain external characters in common that are visible on superficial 

 examination. 



The form and disposition of the branchiae are shown in the following table — 



Pleurobranohiae, . . . 1 1 1 1 



Arthrobranchise, . . . 



Podobranchije, . . . 



Mastigobranchiae, . . . 1 ... 



h i k 1 la n o 



Observations. — The late Professor Kinahan in a paper on this genus, 1 says of 

 Hippolyte varians : — " This species occurs in great numbers in the sand-pools among 

 the Zostera banks at Sandycove, near Kingstown ; spawns in May. The specimens 

 vary remarkably and beautifully in colour ; pink, red, salmon, emerald -green, cobalt- 

 blue, gray, chocolate-brown, opal white, are among the prevailing tints ; the ova of a 

 chocolate-brown. 



" It is remarkably sensitive of handling ; in no case could I succeed in keeping it 

 for over forty-eight hours in a tank, although specimens of Crangon fasciatus and 

 Mysis chameleon, from the same locality, lived with me for days. A volume might be 

 written on the forms of the beak of this species. I have figured (pi. x.) the best 

 marked varieties, which occurred in the following proportions : — 



" Plate x. fig 1. — a. Normal type ; rostrum nearly straight ; apex bidentate, 

 directed upwards, upper tooth shortest ; below, two teeth, the anterior much posterior to 

 the upper tooth of apex ; proportional frequency of occurrence, 63 per cent. 



" Fig. 2. — b. Rostrum straight ; apex tri-dentate, teeth directed forwards, upper 

 and lower teeth nearly equal in length ; below one tooth only ; proportional frequency, 

 25 per cent. 



" Fig. 3. — c. Rostrum strongly curved upwards, scimitar-shaped ; apex tridentate, 

 upper tooth slightly longer than the lower ; below a single tooth ; proportion, 8 per 

 cent. N.B. — The whole animal is much slenderer than the normal type ; query a 

 species ? 



1 Proc. Nat. Hist. Soc. Dublin, 1857, p. 48. 



