REPORT ON THE CRUSTACEA MACRTJRA. 537 



numerously multiarticulatc, and terminates in a small but apparently efficient chela, 

 generally ovate in form. In Cheirothrix the second pah- of pereiopoda is shorter than the 

 third, the carpos is only a trifle longer than the meros and only five-articulate, and the 

 propodos is as long as the carpos — a feature unknown in Alpheus — and instead of being 

 ovate it gradually tapers from the same diameter as the carpos to a point, which appears to 

 be broken into hairs of unusual and peculiar form as above described. 



It is to be regretted that there is but one specimen, which precludes my being able 

 to examine other and less conspicuous parts. 



Alpheus, Fabricius. 



Alpheus, Fabricius, Suppl. Entorn. Syst., p. 404, 1778. 



,, Risso, Crust, de Nice, p. 88, 181G. 

 Alphxus, Desmarest, Consid. sur les Crust., p. 222, 1825. 

 Alpheus, Milne-Edwards, Hist. Nat. Crust., torn. ii. p. 349. 



This genus was first established by Fabricius, but was not clearly defined until Milne - 

 Edwards described it. 



The whole of the animal is dorsally rounded and laterally compressed ; the ophthal- 

 mopoda are reduced in size, so that they are hidden beneath the anterior region of the 

 carapace, which is so extremely thin over them as to become transparent, thus protecting 

 the eyes without interfering with vision. The rostrum is short and pointed. 



The first pair of antenna? has the peduncle short ; the first joint is flattened, and carries 

 a short stylocerite on the outer side, and the terminal supports two flagella, the inner of 

 which has a tendency to bifurcate. 



The second pair carries a long flagellum and a strong scaphocerite that terminates in 

 a subapical point or sharp tooth. 



The mandibles are robust, furnished with a molar protuberance distinctly separated 

 from the concave and serrate psalistoma, and carry a short three-jointed synaphipod. 



The first pair of gnathopoda is short and five-jointed, the ultimate joint articulated at 

 the inner and posterior angle of the penultimate, and reflexed against its inner margin. 



The second pair of gnathopoda is pediform, five-jointed, subcylindrical, and carries a 

 short and slender basecphysis. 



The first pair of pereiopoda is chelate, carries a large propodos, that on the right side 

 being generally larger than that on the left, and is of a more or less abnormal form 

 especially in the male. The second pair of pereiopoda is slender, minutely chelate, 

 having the carpos long, cybndrical, and multiarticulate. The posterior three pairs are 

 simple and terminate in a short robust dactylos. 



The pleon is short and terminates in a telson that is broad and rounded ; the outer 

 plates of the tail-fan are furnished with a strongly marked diuresis. 



(ZOOL. CHALL. EXP. PART I.II. 1887.) Fff 68 



