Museum, S. I. Smith divided the species of Peneus into two generic groups, 

 namely (1) Peneus proper, with P. caramote and its kind as types, and (2) Para- 

 peneus, typified by P. longirostris Lucas ( = P. memhranaceus of Heller). This 

 arrangement has been accepted by most subsequent authors. 



In 1891, in Vol. VIII (Cth series) of the Annals and Magazine of Natural 

 History, "Wood-Mason took a further step in splitting from Parapeneus a third 

 generic group Matapeneus, with M. affinis Bdw. as the type. Wood-Mason also 

 recognized, among the Penei lying outside the limits of Smith's restricted genus 

 Peneus, that P. siyliferus Edw. constituted a fourth distinct type, to which he 

 gave the MS. name Parapeneopsis. 



In 1896, in the Zoologischer Anzeiger, de Man described a new Peneid, 

 which from the peculiar size and length of the 1st pair of male chelipeds he made 

 the type of a distinct genus Heferopeneus. It now appears from' Nobili's obser- 

 vations, that the difference between Heteropeneus and Peneus is, perhaps, rather 

 less than that between the latter genus and Parapeneiis, Metapeneus, and Para- 

 peneopsis. 



At the present moment the number of valid species appertaining to the 

 Peneus group is, perhaps, about 75. They may be distributed in 8 genera, 

 namely : Peneus (sensu restricto), which is represented all round the globe in 

 tropical and temperate latitudes ; Heferopeneus, which is confined to the Bast 

 Indian Archipelago ; Parapeneus (sensu restricto), whose range extends from 

 the W. Indies and Atlantic coasts of America westwards, through the Medi- 

 terranean, to Oriental seas and the western Pacific, and whose habitat is uectic 

 rather than littoral ; Metapeneus, which, with two doubtful exceptions in the 

 "West Indies, is restricted to the Indo-Pacific; Parapeneopsis, which is also i-e- 

 stricted to the Indo-Pacific ; Xiphope.neus, which is confined to tropical and sub- 

 tropical parts of the Atlantic coast of America ; Trachypeneus, which is found, 

 on the one hand, off the West Indies and the neighbouring coasts of America, 

 and, on the other hand, in Oriental seas from India to Japan; and Atypopeneus, 

 which is known with certainty only from the Bay of Bengal, but perhaps occurs 

 also in the China Sea. 



The following are the diagnostic points common to the whole group : — 



Rostrum well developed, laterally compressed. Carapace with post-anten- 

 nular (antennal) and hepatic spines, sometimes with a small post-ocular (orbital) 

 tooth or spine, and sometimes with a spine (branchiostegal) at or near its antero- 

 inferior angles. The cervical groove is never impressed across the tergum of the 

 carapace. Abdomen long, with some of its posterior somites compressed and 

 their terga carinated. 



Eyes large. Basal joint of antennular peduncle hollowed dorsally to lodge 



1 BoUetino dei Mnsei di Zoologia at Anatomia cotnparata della K. CJniversita di Torino, No. -155, 1903. 



