220 A HISTORY OF EECENT CRUSTACEA 



species of the deep-sea genera, such as Benthesicymus and 

 Gennadas, Spence Bate, the eye-stalk sends out a promi- 

 nently pointed tubercle, with a small circular lens at its 

 extremity, served by a distinct branch of the optic nerve, 

 this single lens being very translucent and without trace 

 of pigment. Gennadas received its name, meaning ' of a 

 noble race/ because it ' approximates nearer than any 

 other to the little crustacean named Penceus (Kolga) spe- 

 ciosus in Salter and Woodward's map of fossil Crustacea.' 



Peteinura, Spence Bate, 1888, meaning < flying- tail,' is 

 established for a single species Peteinura gubernata (see 

 Plate IX.), founded 011 a single specimen an inch long, taken 

 at the surface of the Atlantic at night time. There can 

 be no doubt that the supposition is justified that the 

 specimen is an immature form. There is a very long 

 slender rostrum such as is common in larval forms, but 

 the strangest peculiarity is at the other extremity of the 

 animal. The sixth segment of the pleon, which is about 

 as long as the four preceding segments together, carries a 

 pair of uropods of which the inner branch is small and 

 rudimentary, whereas the outer is nearly as large as the 

 rest of the animal, a truly prodigious rudder ! If ever 

 the tail could wag the dog, one might expect a parallel 

 to that phenomenon in this instance. 



Cerataspis, Gray, 1828, of which Cryptopus, Latreille, 

 1829, is a synonym, has been lately shown to have ' almost 

 all the characters of the typical Penaeidae.' Gray referred 

 his Gerataspis monstrosus to the ' Fam. Nebaliadas (Les 

 Schizopodes Latr.),' but Giard and Bonnier say, ' the 

 antennules, the antennae are absolutely those of the 

 Pengeidas ; the second maxilla possesses the four charac- 

 teristic plates ; the endopod of the first maxilliped is five- 

 jointed, the second maxilliped is geniculate, the third is 

 transformed into a locomotive appendage; the thoracic 

 legs are provided with long swimming branches (exopods) ; 

 the first three pairs end in chelas ; the last two are simple, 

 &c.' Referring also to P. J. van Beneden's discovery of 

 the nauplian embryo, they remark that ' among the Schizo- 

 pods the nauplian embryo has only as yet been observed 



