1. '08. 120 



Genus Alpheus, Fabricius. 



Two British species of this genus are known, only one of 

 which has so far been found in Irish waters : — 



I. Frontal portion of carapace evenly rounded from 

 side to side and produced to a short spine in 

 front of each eye, thus giving the anterior 

 margin a tridentate appearance ; external mar- 

 gins of antennal scales slightly concave ; right 

 and left chelae of the first pereiopods closely 

 similar in size and shape, without longitudinal 

 carinae and less than three times as long as 

 wide, the dactylus articulating with the pro- 

 podus by a curious lateral and oblique move- 

 ment, . . . . . .A. macrocheles. 



II. Frontal portion of carapace convex over each eye, 

 the rostrum continued backw^ards as a separate 

 elevation with a groove on either side, anterior 

 margin rounded in front of eyes — not triden- 

 tate ; external margins of antennal scales very 

 strongly concave ; right and left chelae of the 

 first pereiopods very dissimilar in shape and 

 size, the larger nearly four times as long as 

 wide and with four longitudinal carinae, the 

 dactylus articulating normally in both, . A. ruber. 



Alpheus macrocheles (Hailstone) (PL XIX, figs. 3, 4) is not 

 known in Irish waters. It is common in the Mediterranean 

 and has been recorded from the English Channel from the 

 neighbourhood of Hastings, Jersey, Plymouth and Dodman 

 Point. The long and complicated synonymy of this species 

 will be found in Norman and Scott's work (1906) on the Crus- 

 tacea of Devon and Cornwall^. 



Alpheus ruber, H. Milne-Edwards. 

 PI. XIX, figs. 1,2. 



Alpheus ruber, Bell, 1853, fig. p. 271. 

 Alpheus ruber, Norman, 1868 {ubi syn.). 



Colour in life. — The dorsal portions of the carapace and ab- 

 domen are bright red ; the black eyes showing through the 

 semi-transparent frontal margins. The sides of the carapace, 

 abdominal pleura and pleopods are ivory white. The antennal 



1 In addition, Alpheus harhara, Lockington, is, according to Couti^re, 

 probably a synonynfi of this species. A. harhara was found off the coast 

 of California. 



