Observations on Mr. Hailstone's Porcelldna. 269 



jagged. — First pair of legs unequal ; the right, and sometimes 

 the left, being the larger. — Thigh dilated at its internal apex 

 into a blunt lobe. — Wrist with its internal margin, wavy. 

 — Hands compressed, somewhat angular. Claws depressed and 

 twisted, with a few blunt teeth internally. — Shell £ in. long. 



This description is made from a full-grown individual. In 

 what I take to be the young of this species, the lateral mar- 

 gins of the shell are toothed, the internal apex of the thigh 

 of the first pair of legs is produced into a spine; the wrists 

 are spinulose with two prominent spines on their inner mar- 

 gin ; these last-mentioned spines gradually become lobes, and, 

 at last, a mere wavy outline. In the middle-sized speci- 

 mens, the hands are very rough with scales, giving the mar- 

 gin, especially the outer one, a denticulated appearance. In 

 the full-grown ones they are quite smooth. 



Very common in corallines brought up from deep water. 

 In July last I found a female with spawn. During the last 

 few weeks I have examined several dozens without finding 

 any with spawn. — S. Hailstone. Hastings? Feb. 18. 1835. 



[Observations, by Mr. TVestwood, on the Specimens of, and 

 "Remarks on, a Species of Porcelldna sent by Mr. Hailstone."] — ■ 

 With respect to the gradual series of specimens of Porcellana 

 recently sent you by Mr. Hailstone, and exhibiting the changes 

 undergone by this species in its progress to maturity, I beg 

 to notice that they offer another instance of the necessity of 

 more extended observation, before we can feel ourselves in a 

 situation to place implicit confidence in the researches of Mr. 

 Thompson, as at present developed. 



In a list of memoirs proposed to be published by this 

 gentleman, we find No. 13. to be upon "The Structure and 

 Metamorphoses of the Genus Porcellana of the Crustacea 

 with its new and singular Larva." Now, the smallest specimen 

 sent by Mr. Hailstone is scarcely larger than a large pin's 

 head, its length being represented^. 29. a ; so that, taken in 

 conjunction with its comparatively perfect organisation, and the 

 continued, although slight, changes which the species subse- 

 quently undergoes, it seems impossible to conceive that its 

 form can have materially altered since it left the egg. b 

 shows the length of the next-sized specimen, which at c is 

 represented in a magnified state. Here the large size of the 

 external foot-jaws, the teeth on the wrists, and the small spi- 

 nose internal production of the anterior thighs, are noticeable. 

 The shell is also somewhat longer, in proportion to its width, 

 than at a more mature period. This and the preceding state 

 differ only in the smaller individual being still rather more 

 oblong. Fig. 29. d represents one of the external foot-jaws, 



t 3 



