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CYCLOMETOPA. 

 Family Xanthiclw. 



Sub-family Xanthinse. 

 Okphnoxaj^thus, Alcock. 



Orphnoxanthus, Alcock, J. A. S. B. Vol. LXVII. pt. 2, 1898, p. 127. 



Carapace, owing to the inflation of the branchial regions almost quadrilateral 

 in outline and almost concave from side to side, but very decidedly convex fore 

 and aft, broad, the regions well defined but not to any great extent areolated. 



Fronto-orbital border a Httle more than half the greatest breadth of the 

 carapace in extent. Front about a third the greatest width of the carapace, 

 lamellar, projecting horizontally beyond the orbits, broadly and faintly bilobed. 

 Orbital margin entire : orbits and eyes small. 



Antero-lateral border cut into four teeth ; postero-lateral borders convergent 

 only in the posterior half; posterior border long. 



The antennules fold almost transversely. The basal antenna-joint is very 

 short and only just touches the turned down edge of the front ; the flagellum 

 which is very long (between 2 and 3 times the length of the orbit) is lodged in 

 the narrow orbital hiatus. 



Owing to the bulge of the outer wall of the efferent branchial canal and the 

 consequent puffing out of the pterygostomian regions, the front edge of the 

 merus of the external maxillipeds is quite transverse or even sUghtly oblique from 

 without inwards and backwards. 



The chelipeds are massive and unequal ; the fingers are compressed and 

 pointed. The legs are very slender. 



The abdomen of the male consists of 5 segments, the 3rd-5th somites 

 being fused. 



Owing to the inflation of the pterygostomian regions the efferent branchial 

 channels are permanently open, but the low crests that define them are confined 

 to the posterior part of the endostome. 



This genus appears to represent one of the links between Galene and Xantho. 

 The single known species comes from the Bay of Bengal, 105-350 fms. 



OrjyhnOXanthiiS microps, Alcock and Anderson. 



Xanthodes microps, Alcock and Anderson, J. A. S. B. Vol. LXIII. pt. 2. 1894, p. 183. 



Orphnoxanthus „ncrops, Alcock, J. A. S. B. Vol. LXVII. pt. 2, 1898, p. 128. and 111. Zool. Investigator, Crust. 

 jil. xxxvi. fig. 8. 



Carapace about f as long as broad, almost quadrilateral in outline, strongly 

 convex fore and aft, but, owing to the inflation of the branchial regions, a httle 

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