126 THE VOYAGE OF H.M.S. CHALLENGER. 



being directed upwards (PI. XIX. fig. c, ot), the extremity of the organ rests against the 

 under surface of the first joint of the first pair of antennas (fig. C"), producing a depres- 

 sion on the surface. 



As I have previously stated, the desire not to injure this interesting and unique 

 specimen has kept me from examining the oral appendages. 



The second pair of gnathopoda and the succeeding pereiopoda closely resemble 

 in proportion and general character the corresponding appendages in the genus 

 Pentacheles. 



The pleon differs in being considerably narrower than is generally the case in species 

 of the Eryonidee, of which, so far as I am aware, there are only two resembling it, namely, 

 the recent Polycheles rosea, and the fossil Eryon cuvieri. It may, therefore, be con- 

 sidered that this form, whether immature or fully developed, adds another link to the 

 connection between the recent and fossil Eryonidse. 



Polycheles, Heller. 



Polycheles, Heller, Crustaceen des sudlichen Europa, p. 209, 1863. 



,, Sp. B., Ann. and Mag. Nat. Hist., ser. 5, vol. ii. p. 276, 1878. 



Dorsal surface of the carapace flattened and depressed. Latero-anterior angles 

 projecting beyond the anterior margin. Pleon not longer than the carapace. Ophthal- 

 mopoda obscure, immovably lodged in an orbit excavated in the dorso-frontal margin of 

 the carapace, more or less covered by the antero-lateral margin of the carapace. 



First pair of antennae furnished with two long slender flagella, of which the outer is 

 the shorter. 



Second pair of antennae having a scaphocerite, and terminating in a long and slender 

 flagellum ; four anterior pairs of pereiopoda chelate, the anterior being the largest, and 

 the fifth pair in the male terminating in a simple styliform dactylos. 



First pair of pleopoda in the male having a long and slender biarticulate stalk, 

 terminating in a broad and spoon-like extremity ; in the female, biarticulate, slender and 

 feeble throughout. 



The second and four posterior pairs biramose, the branches fringed with long ciliated 

 hairs, the inner branch, in the male, supporting two subequal stylamblydes, in the 

 female, one. 



The rhipidura is symmetrical and well developed, outer branch broad. Telson 

 tapering. 



Geographical Distribution. — This genus ranges from the Mediterranean to the West 

 Indies. Heller's typical species, Polycheles typhlops, was first taken off the coast of Sicily, 

 and by the Rev. Dr. Norman off the Portuguese coast, and Polycheles sculptus, S. Smith, 

 was obtained in 250 fathoms off the coast of Nova Scotia ; while other species are 



