170 CEYLON PEARL OYSTER REPORT. 



The telson (fig. 9) has the six marginal spines well developed, unusually stout and 

 blunt. In the largest specimen the lateral spines are almost obsolete. The sub- 

 median spines have a small movable spinule at their tips. There are no submedian, 

 intermediate, or lateral denticles whatever. The dorsal surface of the telson bears a 

 median, broadly oval carina, and a narrower and rather sharper carina on each side of 

 it. There is also a prominent carina running down into the submedian and inter- 

 mediate spines of the telson. The median carina bears at its posterior end a prominent 

 blunt spine, with two small blunt tubercles on each side of it. The lateral carinae 

 and those which run into the intermediate and submedian spines of the telson are 

 broken up into irregular tubercles. The lateral carinse and those of the intermediate 

 spines are composed of three of the tubercles, those of the submedian spines of four, 

 which are moreover rounder and more regular in shape. 



The uropods (fig. 10) are very powerfully built. The basal joint bears a very 

 prominent dorsal ridge, which is continued down both joints of the exopod. These 

 joints are therefore triangular in cross section. The first joint of the exopod bears 

 eleven stout spines on its outer edge. Both paddles are unusually tough and 

 chitinous, and quite unlike the flat, thin, membranaceous, lamella-like paddle usually 

 met with in Stomatopods. Both have prominent dorsal ridges, and the inner one is 

 of a most unusual scythe shape (fig. 10). DE MAN figures a similar paddle to the 

 inner uropod of G. drepanephorus. The setse are mostly broken off. 



Length of the largest specimen 28 millims. 



The colour of the preserved specimens is generally pale, but there is a distribution 

 of black pigment, which is the same for both specimens. There are three prominent 

 black pigment spots on the posterior part of the carapace, surrounded by numerous 

 pigment flecks. Anterior to these, on each side, on the suture separating the median 

 from the lateral parts of the carapace, is a small, narrowly oval, pigmented area. 

 There is a prominent median black pigment spot surrounded by numerous pigment 

 flecks in the ante-penultimate thoracic and first, third, fourth and fifth abdominal 

 segments, while scattered pigment flecks are to be seen on the lateral parts of all the 

 abdominal segments. 



Four species of Gonodactylus have been described with a Protosquilla-like rostrum, 

 viz., G. acutirostris, DE MAN, G. drepanephorus, DE MAN, G. festa, NOBILI, and 

 G. demani, HENDERSON. From all these G. herdmani is at once distinguished by the 

 unusual bluntness and stoutness of the marginal spines of the telson, the presence of 

 a movable spinule at the tip of the submedian spines, and the complete absence of sub- 

 median, intermediate, or lateral denticles on the telson. Its nearest relative is 

 G. drepanephorus, which has the same peculiar paddle to the endopodite of the 

 uropods, but the spines on the telson of the latter are much sharper and more 

 numerous than in G. herdmani, while the tubercles on the sixth segment end in 

 spines, whereas in the present species these tubercles are quite smooth. 



I have named the species in honour of its discoverer. 



