REPORT ON THE CRUSTACEA MACRURA. 483 



PontophUus with Orangon, and Kinahan ' more recently established his several genera 

 on features that are liable to vary. 



Development (PL LXXXVI. fig. 4 ; PL LXXXIX. fig. 1).— The brephalos of Crangon, 

 as it quits the ovum, exists in a form not very unlike that of the Zoea of Palsemon. 



It has the carapace anteriorly produced to a sharp-pointed rostrum that is about one- 

 third the length of the carapace, but exhibits signs that at its first moult the anterior 

 extremity is lost. The pleon has the posterior margins of the third somite dorsally 

 armed in the median line with a sharp-pointed tooth, and the fifth somite with one on 

 each side of the dorsal surface. The sixth somite is longer than the preceding two, and 

 continuous with the broad and fan-like telson (fig. 4z), the distal margin of which is 

 fringed with seven cfliated spines on each side. 



The ophthalmopod exists chiefly as a large ophthalmus, being nearly equal in depth 

 and in breadth, subequal in length to that of the carapace. 



The first pair of antennae consists of a single jointed peduncle that extends beyond the 

 end of the rostrum and terminates in two small flagella, rudimentary in character and 

 tipped with hairs. 



The second pair of antennse has the peduncle consisting of two distinct joints, the 

 extremity of which supports two branches ; one, narrow and sharp pointed, represents 

 the future flagellum, the other, broad and distally fringed with hairs, the scaphocerite. 



The mandibles are not very dissimilar to those of the adult, and the same is true of 

 the siagnopoda. 



The gnathopoda are pediform and seven-jointed, the second joint carrying a long 

 basecphysis, and the seventh tipped with three cdiated hairs. 



Four pairs of pereiopoda exist as sac-like buds. 



The pleopoda are also in an incipient condition. 



Geographical Distribution. — The range of this genus is very great, but so far as I 

 am aware, it is confined to the northern hemisphere. It is found on the sandy shores all 

 round the coasts of Europe, and we have frequently taken an unspotted variety off the 

 coasts of Devon and Cornwall, in from 10 to 50 fathoms of water. Dana records it from 

 the western coasts of North America, from San Francisco, California, and Puget's Sound. 

 Dr. Stimpson recognised a variety from the Pacific coast of North America as a distinct 

 species from Crangon vulgaris, under the name of Crangon nigricauda, but as its 

 distinction chiefly rests on the colour of the caudal extremity, with very minor and un- 

 important structural variations, it can scarcely be accepted as forming a distinct species. 

 Crangon propinquus, Stimpson, which I also believe to belong to this species, was obtained 

 off the northern shores of Japan. He says that it differs both from Crangon vulgaris 

 and Crangon nigricauda only in having the fourth somite of the pleon, and sometimes 

 the third also, carinated in the adult. 



1 Proc. Roy. Irish Acad., p. 354. 1862. 



