138 ME. G. M. THOMSON ON THE NEW ZEALAND 



2. Alpueus xov.e-zealaxdi.e, Miers. 



1S7G. Micrs, Ann. & 'Slag. Nat. Hist. ser. 4, xvii. p. ;224 ; Cat. N.Z. Crust, p. 82, pi. 2. fig. 2. 



I do not know tbi.s species. Miers savs it " is distiugui-shed by the absence of spinules 

 on the upper orbital margin, the shorter basal spine of the external antennte, ^c," — 

 characters almost too indetemiinate to found a specific distinction upon. 



Genus 2. Bet-EUS, Dana, 1852. 



It is difficult to find a definite character on -SThich to base the generic distinction 

 between Betceus and Alphens. The two points emphasized by Dana are the absence of a 

 rostrum and the inverted position of the propodos of the first pereiopods. But Stimpson 

 gives as tlie principal character of the Australian B. trispinosus, " front with a long 

 needle-like ro.strum, and armed with two acute orbital teeth, which are half the length 

 of the rostrum." In our Xew Zealand species these orbital teeth are present, though 

 small, and are not on the margin of the carapace, but on the front of the eyes. The 

 t«i.sting of the first pereiopods, by which tlie dactylos is on the lower side of the propodos, 

 appears to me to be due to a slight twisting of all three joints — the meros, carpos, and 

 especially the propodos. 



The ova, as pointed out by Sjjcnce Bate (Chall. Macr. p. 564), are much larger and 

 more oval than the small spherical ova of Alphens. The only New Zealand species 

 appears to be very distinct. Spence Bate, considering a mutilated specimen of an 

 Australian species, B. microslyhis, was inclined to assign it to B. (equimanus, but his 

 figures are conclusive against this identification. 



1. Betjels iEQUiMANis, Daua. (Plate 28. figs. 1, 2.) 



18i32. Dana, T'.S. Explor. Exped. xiii., Crust, part i. p. JGO, pi. 3.j. fig. 11. 

 1876. :\Iier.s, Cat. N.Z. Crust, p. 8."i. 



The front of the carapace is notched about as deep as the eye-sockets (tig. 1), above 

 which it rises slightly, and is again slightly notched beneath tlsem ; its antero-inferior 

 angle is rounded. The posterior margin is somewhat convex and acutely notched on 

 each side of the dorsal surface, the postero-lateral portions being produced backwards 

 into a rounded lobe; which lies under the first segment of the pleou. 



The second segment of the plcon has the sides greatly produced both forwards and 

 backwards. 



The tclson (fig. 2) is wedge-shaped, its apex ending in a bkmt tooth on each side, with 

 a somewhat rounded portion between, bearing a row of plumose setse. 



The ophthahuopods are short, depressed, and slightly projecting from under the front 

 of the cara2)ace ; the eyes are nearly circular, and occupy the greater portion of their 

 upper surface. In front they are produced into a small spinule. 



The first antenna^ have the joints of the peduncle subequal in length and diameter, the 

 first being slightly the longest. The basal scale reaches to the extremity of the second 

 joint. 'J'he outer short nagellum shows the normal tendency to divide into two at the apex. 



