134 Memoirs of the Indian Museum. [Voi,. IV, 



spinules), one or two intermediate denticles and one lateral. Ventral process of 

 uropods terminating in two sharp spines, inner usually shorter than outer. 



There are no well-marked secondary sexual distinctions. 



Ten species of this genus are known ; nine have been found in Indo-pacific 

 waters and one, 0. havanensis , in the Atlantic. No species is known to inhabit both 

 areas. 



Specimens of Odontodactylus are, unfortunately, not numerous in collections 

 and consequently little is known of the variation that occurs within the limits of 

 the species and of the alteration in form due to growth. In taxonomic work the 

 precise number and disposition of the carinae on the telson is of great importance, 

 but this is a character that may perhaps be modified in the course of growth from the 

 post-larval form to the adult. Another feature which appears to have considerable 

 systematic value is the size of the eye. In S quitta the breadth of the cornea is 

 known to decrease proportionately during growth and this, if true in Odontodactylus, 

 must have much influence on our views of the limits of the various species. Exami- 

 nation of seven specimens of 0. southwelli , varying from 21 to 37 mm. in length, 

 seems, however, to indicate that this proportional difference, due to growth, is not 

 one of any considerable magnitude, at any rate in that form. 



The species appear to live on rough ground, but of their habits nothing precise 

 is known. The greatest depth from which any member of the genus has been 

 obtained is 163 fathoms (0. havanensis , Bigelow). 



For explanation of the terminology used below in designating the carinae of the 

 telson, see text- fig. 4, p. 12. 



Key to the species of Odontodactylus. 



I. Dactylus of raptorial claw with only two or three teeth on its inner margin. 



A. Several carinae on sixth abdominal somite, six of them terminating pos- 



teriorly in spines ; several carinae in anterior half of telson on either side 

 of median crest. 

 I. Raptorial dactylus with two teeth ; second lateral carinae of telson 

 present. 



A. Breadth of cornea about one- fifth median length of carapace ; raptorial 



dactylus very strongly dilated at base ; median crest of telson not 



remarkably high, with two pairs of submedian carinae . . . . scyttarus, p. 135. 



B. Breadth of cornea about one- third median length of carapace ; rapto- 



rial dactylus not very strongly dilated at base ; median crest of telson 

 remarkably high with a single pair of submedian carinae . . cullrifer, p. 137, 



II. Raptorial dactylus with three teeth ; second lateral carinae of telson ab- 

 sent (breadth of cornea about one half median length of carapace) . . carinifer, p. 138. 



B. Sixth abdominal somite without carinae, with only four posterior spines, 



submedians and postero-laterals ; telson with median carina only . . elegans, p. 139. 



I. Dactylus of raptorial claw with at least six teeth on its inner margin. 

 A. Second lateral carina of telson present. 



I. Telson with two pairs of submedian carinae ; second lateral carina run- 

 ning to apex of lateral marginal tooth (text-fig. 4, p. 12) . . japonicus, p. 13g. 

 II. Telson with a single pair of submedian carinae ; second lateral carina 



