CLASS I. CRUSTACEA. 103 



Genus 5. LEUCOTIIOE. Leach. 

 Anterior pair of legs didactyle; the thumb biarticulatc : second pair with 



a dilated and compressed hand, furnished with a crooked thumb. 

 Sp. 1. Leu. articulosa. 

 Cancer articulosus. Montagu, Trans. Linn.Soc. vii. 71. t. 6.f. 6. Leu- 



cothoe articulosa. Leach, Edin. Encyct. \'ii. 403. — Trans. Linn. Soc. 



xi. 358. — Supp. to Enci/cl. Brit. i. 425. 

 Inhabits the British sea, but is very rare. 



Stirps 3. — Antenna" {our-jo'intcd, the last segment composed of several 

 little joints; upper ones longest. 



Subdivision 1. — Four anterior legs monodacti/Ie, second pair with a much 



dilated compressed hand. 

 Genus G. MELITA. Leach. 



Anterior pair of legs monodactyle* second pair with the thumb inflexed 

 on the palm: tail on each side with an elongate foliaceous lamella. 



Sp. 1. Mel. palmata. Body blackish : antennae and legs annulated with 

 pale colour. 



Cancer palmatus. Montagu, Trans. Linn. Soc. vii. G9. Melita palma- 

 ta. Leach, Edin. Encycl. vii. 403. — Trans. Linn. Soc. xi. 358. — Supp. to 

 Encycl. Brit. i. 4'25. pi. '21. 



Inhabits the sea shore on the Devonshire coast under stones. 



Genus 7. M.^RA. Leach. 

 Four anterior kgs didactj'lc ; thumb of the second pair bent on the side 



of the hand: tail with no foliaceous appendices. 

 Sp. 1. j\Iie. gi'ossiinana. 

 Cancer Gammarus grossimanus. Montagu, Trans. Linn. Soc. ix. 97. t. 4. 



f. 5. INIsera grossimana. Leach, Edin. Enci/cl.\n.iOZ. — Trans. Linn. 



Soc.\\. 359. — Supp. to Encjjcl. Brit. i. 425. 

 Inhabits the southern coast of Devonshire beneath stones. 



Subdivision 2. — Tico anterior pair of legs itwnodacti/le and alike. 

 Genus 8. GAMMARUS. Latr., Leach. 

 Superior antenme furnished at the base of the fourth joint with a little 

 jointed seta : t(ul aijove with bundles of spines. 



* Tail with the superior double styles, having the upper style process 

 •rery short. 

 Sp. 1. Gam. acjuaticus. Process between the antennae rounded, obtuse. 

 Gammarus Pulex. Leach, Edin. Encycl. vii. 402 — 432. Gammarus aqua- 

 ticus. Leach, T-ans. Linn.Soc. xi. '3o9. — Supp. to Encycl. Brit.i. 425. 

 Inhabits ponds, ditches, and springs in great plenty. 

 Sp. 2. Gam. marinus. Process bet^veen the antenna" subacuminate. 

 Gammarus marinus. Leach, Trans. Linn. Soc. xi. 359. — Supp.to Encyclt 



Brit. i. 425. 

 Inhabits the sea on the southern coast of Devonshire in plenty. 



