TO INDIAN CAECINOLOGT. U7 



to that genus, as restricted by Prof. S. J. Smith ; most of the species are probably 

 referable to Parapenceus, Smith, which is characterized chiefly by the absence of 

 branchiae from the last thoracic segment *. A revision of the Penseidae, based on a 

 large collection both of shallow-water and deep-water forms, is much needed, for at 

 present the genera are in a state of considerable confusion, and Spence Bate appears to 

 have worked independently of the results previously arrived at by Smith. Too much 

 stress has perhaps been laid on certain features of the branchial arrangement, as, for 

 instance, the number of epipodites, in drawing up generic characters. 



269. Pen^tjs monodon, Pabr. 



P. monodon (Fabr.), Bate, 'Challenger' Macrura, p. 250, pi. xxxiv. fig. 1 (1888). 



( = P. semisulcatus, De Haan). 



Bombay, Madras, Ganjam, many specimens (Day) ; very common on the South 

 Indian coast and the chief edible species (J. R. H.). 



The rostrum is about equal to the antenna! peduncles, though sometimes longer, and 

 is continued as a sulcate ridge almost to the hind margin of the carapace ; the tooth- 

 formula is j-^g, with usually three teeth below. The antennular flagella are about 



equal in length to the peduncle. A short longitudiual ridge occurs on the carapace 

 below the hepatic spine, and parallel to the free margin. The basal joint of the first 

 legs is bispinose, that of the second legs unispinose. The fourth, fifth, and sixth 

 abdominal segments are carinated. The species reaches a length of about a foot. 

 P. tahitensis, Heller, and P. carinatus, Dana, are perhaps referable to this species. 



Distribution. Prom the Red Sea and E. Africa to Japan, Australia, and the Pacific 

 (Pijis). 



•270. Pen^etjs indicus, Milne-Edw. 



P. indicus (Milne-Edw.), Bate, ' Challenger' Macrura, p. 249, pi. xxxiii. fig. 2 (1888). 



(= I', merguiensis, De Man). 



Kurachi, Madras, Ganjam, Calcutta, Akyab, many specimens (Lai/) ; very common at 

 Madras [J. B. H.). 



The rostrum is styliform distally, and varies considerably in length ; in young- 

 examples it is usually considerably longer than the antennular peduncles, whereas in 

 adults it is generally shorter than in the young, and is continued as a prominent crest to 



about the middle of the carapace ; the tooth-formula is ^^, with, as a rule, four to six 



small teeth below. On the carapace the rostrum forms a faint and obscurely sulcate ridge 

 posteriorly, which, however, does not reach the hind margin. The antenimlar flagella 



* The genus Metapenceus, Wood-Mason (Ann. Mag. .Nat. Hist. ser. 6, vol. viii. p. 271, 1891), is separated from 

 Parapenams by very slight characters, the most important of which is the presence of a rudimentary anterior 

 arthrobranch on the penultimate thoracic segment, a character which is absent in one of the species referred by 

 Wood-Mason to the genus. 



03* 



