536 



PYCNOGONIDA 



differs from Aminotheidae in the possession of a claw on appen- 

 dage III. It is highly peculiar in the structure of the mouth, 

 in having a long forward extension of the oculiferous tuhercle 

 jutting out over the proboscis, in the extreme shortness of the 

 intestinal caeca and ovaries which scarcely extend into the legs, 

 and in the absence of cement-glands from the fourth joint of the 

 legs ; these last are present only in the third joint of the pen- 

 ultimate legs. A single pair of generative orifices are found on 



Fio. 284. Rhynclwthorax mediterraneus, Costa. A, Body and bases of legs ; 

 B, terminal joints of palp. (After Dohrn.) 



the last legs. A second species, R. australis, Hodgson, comes 

 from the Antarctic. 



Fam. 6. Nymphonidae. Appendage I. well -developed, 

 chelate ; II. well - developed, usually 5 -jointed; III. well- 

 developed in both sexes, usually 10-jointed, the terminal joints 

 with one row of denticulated spines. 



Nymphon, Fabr. (1794), about forty-five recognised species, 

 of which some are but narrowly defined. Closely allied are 

 Chaetonymplion, G. 0. Sars (1888), including thick -set, hairy 

 species, about eight in number, from the North Atlantic, Arctic, 

 and Antarctic; and Boreonymplion, G. 0. Sars (1888), with one 

 species (B. robustum, Bell, Fig. 276), also northern, in which the 

 auxiliary claws are almost absent. Nymphon brevicaudatum, 



