152 Mr. C. SpenceBate on British Edriophthalmous Crustacea' 



of each except the last. Head vaulted, craniform. In the female, 

 the Bpioes are reduced to tubercles. 

 Drake's Island, G. Barlee, Esq. 



Genus 4. Cyamus (Latreille). 

 Head small, body depressed. Abdomen rudimentary. Third 

 and fourth pereiopoda rudimentary. Inferior antenna rudi- 

 mentary. Parasitic. 



1. C. Ce/i (Linnseus). Body moderately developed. Branchiae 



simple, furnished at the base with two unequal and pointed 

 appendages. 



2. C. ovalis (Roussel de Vauzeme). Body very large. Four 



pairs of branchiae to both sexes ; those of the third segment 

 have a solitary appendage, while those of the fourth have two. 



3. C. gracilis (Roussel de Vauzeme). Body slight and narrow. 



4. C. ? 



C. gracilis (Gosse). 



Bi "^ ^ 



A. Head. B. Pereion. B 1. Anterior pereion. B2. Posterior pereion. 

 C. Pleon. CI. Anterior pleon. C2. Posterior pleon. 1. Upper 

 antenna. 2. Lower antenna, a. Olfactory denticle, p. Peduncle. 

 /. Filament, cf. Complementary or secondary filament. 3. Palp of 

 mandible. 4. Maxilliped. b^Q. Gnathopoda. 7 to 11 . Pereiopoda. 

 12, 13, 14. Anterior pleopoda. 15, 16, 17- Posterior pleopoda. 18. 

 Telson*. 



Propodos. 

 Dactylos. 



These terms are abbreviated from M. Milne-Edwards. 



* The terms used in this paper are suggested instead of the old and 

 incorrect synonyms of thorax, abdomen, &c., which authors frequently 

 employ to signify diiFerent parts of the animal. 



