172 CEYLON PEARL OYSTER REPORT. 



A figure of the endopodite of the first abdominal appendage of the male (fig. 13) 

 is given for comparison with other species. 



Length of the type male 8 millims., of the type female 10 millims. 



The colour of the preserved specimens is uniformly pale, with rather a characteristic 

 group of chromatophores on the first abdominal segment, and a less distinct group 

 on the ante-penultimate thoracic segment. 



This species of Gonodactylus is abundantly distinguished from all known species 

 of the genus by the spinous inner margin of both paddles of the uropods, as well 

 as by the rather distinctive armature of the telson. 



Odontodactylus brevirostris (Miers, 1884). Plate II., figs. 16 to 18. 



Locality : Pearl Banks, Gulf of Manaar. One female, 16 millims. 



I have thought it advisable to give a brief description of the single Ceylon example. 



The rostrum (fig. 16) is rather more than twice as wide as long, quite smooth, not 

 sinuate but transverse, and evenly rounded in outline. The centre of the anterior 

 margin is, however, slightly depressed, so that the rostrum, in situ, appears to be 

 slightly emarginate (fig. 17). 



The carapace is rectangular in outline, of about equal width throughout and having 

 its antero-lateral and postero-lateral angles rounded. 



The lateral parts of the last three thoracic segments are rounded. 



The abdomen is of about equal width throughout. The postero-lateral angles of 

 the first three segments are rounded, those of the fourth and fifth produced into 

 short acute spines. The first five segments are quite smooth and devoid of all 

 carinas and ridges. The sixth segment bears six rather sharp carinas, all of which 

 end posteriorly in acute spines. There is also a small tubercle on each side of the 

 sixth segment between the intermediate and lateral carinas. 



There is no spine at the articulation of the uropods. 



The telson has the six marginal spines well developed, long and acute, the sub- 

 median ones with a movable spinule at their tips. There are sixteen submedian 

 two intermediate, and a single lateral denticle on each side. The dorsal surface bears 

 a median crest and four other rather sharp carinas. The dorsal crest is interrupted 

 slightly at its anterior end, and posteriorly it ends in a prominent spine. The carina 

 on each side of the crest is very low and does not end posteriorly in a spine. The 

 lateral carinas are more elevated than the intermediate ones and not spinous posteriorly. 

 There is also a prominent carina running into the submedian spines. 



The uropods have the outer spine of the basal prolongation longer than the inner 

 and reaching to the level of the tips of the submedian spines of the telson. The 

 basal joint of the exopod bears ten strong movable spines on its outer edge. 



The raptorial claw (fig. 18) has the dactylus very little ventricose at its base and 

 provided with seven spines on its internal margin in addition to the terminal one. 



Length 16 millims. 



