CRUSTACEANS 



common, species of the Malacostracous animals that inhabit our coasts ; it is taken by digging 

 beneath the sand at low-water mark, and is found thrown on all the sandy shores of Great Britain 

 in great abundance, especially during storms. The very fine specimens presented in the annexed 

 plate were given to me by my indefatigable friend, C. Prideaux, Esq., along with a vast number of 

 rare and curious Crustacea, taken by himself on the southern coast of Devonshire.'^ It occurs also 

 on the northern coast. Bell and Parfitt deny that this species is by any means common within 

 their experience, and the Marine Biological Association omits it entirely without comment 

 from its list in 1 904. The Association, however, adds to the fauna of Devon Portumnus biguttatus, 

 described and figured by Risso in 1816, and later recorded by several authors as Platyonichus 

 (or Platyonychus) nasutus, the specific name alluding to its very prominent interorbital 'front.' 

 Risso states that the carapace is yellowish white, with two great blotches of coral red, while O. G. 

 Costa supplies the useful warning that these distinctive blotches vanish after death, and Garstang 

 thinks ' it is possible that these spots are only to be observed in the breeding season, and that 

 they are due to the colour of the reproductive glands showing through the carapace.'* The 

 Association record speaks of occasional specimens burrowing in fine gravel at Drake's Island; 

 females in berry, and the megalops stage being observed in August. The same trustworthy register 

 says of Polybius henslowii that ' the $ is not uncommon at times on the shrimp-trawling grounds, 

 particularly in Cawsand B., also swimming near the surface at the deep water stations, but the 

 S has only twice been recorded at the Laboratory.' Females were observed in berry, and the 

 young were hatched, in September. 



Pirimela denticu/ata, though first described by Montagu, was not first found in Devonshire. The 

 genus in which it now stands was established by Leach, and must not be confounded with the 

 botanical Pr/nza/a, as the preliminary list of the Marine Biological Association in 1888 might lead 

 the unwary to suppose.' Leach says of this species, ' Dead examples were found at Bantham on 

 the south coast of Devon, by C. Prideaux, Esq., who, with his usual liberality, supplied my cabinet 

 with a fine series, exhibiting considerable variation in colour ; but the finest individual that I have seen, 

 and which is figured in the adjoining plate, was found amongst the rubbish of some trawl-fishers at 

 Torquay by that accurate observer of nature, Dr. Goodall, Provost of Eton, who gave it to me 

 with a number of other marine productions that now enrich my cabinet.' * 



Atelecydus septerpdentatus hails originally from this county. Like the preceding species it owes 

 its generic name to Leach, and the specific to Montagu, who first described, as he was also the first 

 to find it. His description of it was read at the Linnean Society on 7 April, 1807, and begins 

 with a statement explanatory of its name, ' Thorax suborbicular, smooth, with a slightly embossed, 

 urn-shaped impression : front obtuse, tridentate, the sides serrated with seven denticulations each, 

 besides those which guard the eyes.' ' The author must have felt somewhat aggrieved that his 

 paper should not have been published till six years after it had been read. His species indeed ran a 

 narrow chance of forfeiting its name, since Leach, who accepted septemdentatm in his earlier 

 writings, in 1 8 1 5 took the liberty of changing it without adequate reason into heterodon. 



The intelligent reader no doubt accepts in a general way the aphorism that nature does 

 nothing in vain. Nevertheless this vague faith has allowed thousands of naturalists to contemplate 

 the marginal teeth of the carapace in cyclometopous crabs, and to use them freely for generic and 

 specific discrimination, without going on to inquire what meaning or functional value these ' dents,' 

 as Dana has called them, with all their diversity in number, width, slope, and acuteness, may have 

 for the crabs themselves. Mr. Walter Garstang, however, working at the Plymouth station, has 

 redeemed the investigation from the reproach of its long neglect. In his exceedingly interesting 

 paper he says, ' So far as I am aware no one has hitherto elucidated the remarkable constancy of 

 antero-lateral serrations of the carapace in this group of crabs. I here present evidence which tends to 

 show that the presence of conspicuous serrations on these margins of the carapace is functionally related 

 to the exigencies of respiration when these animals are buried in sand.' ® For the method by which 

 representative species of Batiynectes, Atelecydus, and Portumnus, were induced to give up the intimate 

 secret of how to breathe in a situation seemingly so inconvenient, recourse must be had to 

 Mr. Garstang's own ingenious exposition. The same writer has thrown instructive light upon the 

 habits and respiratory mechanism of Corystes cassivelaunus, a species in which the elongate, hair- 

 fringed, geniculating second antennae are so notable a feature. 



Concerning Goneplax rhomboides Leach records an observation by Cranch, that these crabs 

 • live in excavations formed in the hardened mud, and that their habitations, at the extremities of 

 which they live, are open at each end.^ The long-armed males of this species taken at Torquay, 



' Make. Pod. Brit, text to pi. iv (i March, 181 5). 



" Journ. Mar. Biol. Assoc, (new ser.), iv, 404 (1895-7). ' Ibid. No. 2, p. 170 (1888). 



* Malac. Pod. Brit, text to pi. iii (i March, 18 16). ' Trans. Linn. Soc. Lond. xi, i (18 13). 



« Journ. Mar. Biol. Assoc, (new. ser.), iv, 396 (1895-97). 

 ' Malac. Pod. Brit, text to pi. xiii (i March, 1816). 

 I 257 33 



