CLASS r. CRUSTACEA. 87 



6talk, one-jointed : anterior pair of ki^s unequal : CT/es thick : shell 

 ovate-orbicular, orbiculate-quadrate, or transverse subquadrate. 



All the species of this most interesting genus inliabit the bivalve 

 shells of the acephalous Molluxcu, and were supposed liy the ancients 

 to be consentaneous inmates with the animal, bound Ity mutual in- 

 terest. 



Aristotle supposed them to act as sentinels, and believed that they 

 guarded the Pinna (the animal in whose shell they were iirst observ- 

 ed) from the attacks of its enemies. Rondeletius and some other 

 naturalists held the same opinion. 

 Sp. 1. Pin. Cranchii. Shell orl»iculatc-subquadratc, soft, very smooth,with 

 the sides dilated behind : front straight, obscurely subemarginatc : 

 hands oblong below, and ibe thighs above with a ciliated line: 

 thumb subarcuate: abdomen very broad; the sides of the segment 

 arcuate; the second and following ones distinctly notched ; the fifth 

 segment somewhat broader; the last narrower than the preceding 

 segment. Female. 

 Pinnoteres Cranchii. Leach, Malncosf. Poflopfi. Brit. tab. 14. ftg. 4. .5. 

 The male of this species, which was discovered by Mr. J. Cranch, 

 whose name it bears, is unknown. It is distinguished from P. Pisum 

 (the common species) by the form of the front of the shell, which is 

 straight, and slightly notched ; by the dilated hinder part of the shell, 

 and l)y the abdomen, all the joints of which, excepting the first, are 

 distinctly notched behind. 



** Shell quadrate. Ej/es witli a long peduncle. 



Genus 10. GONOPLAX. Leac/i. Ocypoda. Bosc. 

 Ej/es terminating their peduncle: anterior p/iir of leg.s equal; of the 



male very long ; of the female twice the length of the body : antenna 



half the length of the body, inserted at the internal canthus of the 



eyes. 



The animals of this genus inhabit the ocean, preferring such parts 



as have a slimy l)ottom. They burrow laterally in the clay or slime, 



making two entrances to their hole; entering by one and going out 



by the other. 

 Sp. 1. Gon. hispinosn. Shell on each side with two spines: arms above, 



and wrists internally, with one spine. 

 Cancer angidatus. Penn. Brit. Zool. iv. t.S.f. 10. Fahr. Suppl. Entom. 



Si/st. 341. Ocypoda angulata. Bosc, Hist. Nat. des Crust 1. 198. 



Gonoplaxbispinosa. Jj-ach, Trans. Linn. Soc. xi. 323. — Edin. Enci/cl. 



— Supp. to Enct/cl. Brit. — 2Ial. Podoph. Brit. tab. 13. 

 Inhabits the British sea. It is not uncommon at Salcombe and in 



Plymouth sound; and likewise occurs at Weymouth, and at Red 



Wharf in Andesea. 



