24 MR. R. GURNEY ON THE [May 12, 



2. The Metamorphoses of the Decapod Crustaceans ^geo7i 

 (Crangon) fasciatus Uisso and JEgeon {Crangon) 

 trispinosus (Hailstone). By Robert Gurney, B.A., 



F.Z.S. 



[Received March 2, 1903.] 

 (Plates Y. & VI.*) 



During a residence of nearly a year at Plymouth, I was able to 

 obtain and study a very great variety of Decapod larvae, and 

 among them those of five species of Crangonidee. Of_ these five 

 species, which it will be convenient here to consider as all 

 belonging to the genus Crangon, three, namely Crangon vulgaris, 

 C. spinosus, and C. nanus, have already been fully described by 

 Sars, and G. vulgaris has also attracted the attention of a number 

 of other workers in this field of research. The remaining two 

 species, Crangon tris2miosus and C. fasciatus, have remained 

 hitherto unrecognised. The identity of these larvse was placed 

 beyond all doubt both by hatching them from the egg and hy 

 observing the last moult to the adult form. Attempts at rearing 

 the larva} hatched in the Laboratory were quite unsuccessful, 

 though with the same methods (plunger jars) and under 

 apparently similar conditions I was able to rear the larvfe of 

 Pandalina brevirostris i-ight through to the postlai-val form. 



Description of the Larvce. 

 I. Crangon fasciatus (Risso). 



Length of larva on hatching, exclusive of the rostrum t, 1'8 to 

 2"05 mm. Average of 24 specimens 2*0 mm. The rostrum 

 measures about "17 mm. at this stage. 



The general form of the body is slender, the abdominal segments 

 being not distinctly narrower than the thorax. The carapace is 

 prolonged anteriorly into a slender, pointed rostrum, reaching 

 about half the length of the peduncle of the first antenna. Below, 

 its margin is evenly arched and without teeth, ending in front, at 

 the base of the second antenna, in a blunt process. There is no 

 fold of the carapace over the eyes, so that the latter appear as 

 prominent facetted areas of the carapace itself (see Williamson, 

 1901, p. 113). In front of the eyes, and on either side of the 

 rostrum, is a small knob-like process (see PI. V. fig. 1). I can find 



* For explanation of the Plates, see p. 30. 



t As here, so in the case of C. trispinosus the rostrum is left out of account, as 

 measurements from the anterior edge of the eye to the edge of the lateral lobe of the 

 tail-plate give a truer basis of comparison for body-length of different species. 



