1909.] ox DECAPOD CRUSTACEA FROM CHRISTMAS ISLAND. 703 



Eutherian condition of the postcaval vein. Furthermore the two 

 veins may be compai'ed with the Didjelphys embryo figured by 

 McOhire*, where the right cardinal collateral is immensely larger 

 than the left-hand vein. This is one among many variations 

 which occur in the venous system of the embryos, as well as the 

 adults, of that marsupial. Both this variation in Didelphys and 

 the adult condition in Orycterojnis appear to me to be an inter- 

 mediate step in the reduction of the two veins found in 

 Monotremes and Edentates to the single i-ight-hand postrenal 

 postcaval of other Eutheria, 



I now turn to the branches of the postcaval vein. The renals 

 are as is usual asymmetrical, the right-hand veins flowing into 

 the postcaval a little anteriorly to those of the left side. There 

 are two renal veins on each side, and those of the left ai"e 

 connected by an obliquely running joining vessel. Of these two 

 latter vessels the anterior arises from the postcaval vein, where it 

 is single, and the posterior from the slender left postcaval. It is 

 very important to notice, from the point of view of a comparison 

 with other Edentates, that the renals are quite unconnected with 

 the spermatic veins. ISTo recognisable branch appeared accom- 

 panying the ureter. The spermatic veins themselves, as is shown 

 in text-figure 225, are quite symmetrical with each othei* and 

 arise each from its own postcaval vein about half-way down 

 between the i-enal and the posterior bifurcation of the postcaval. 



There is no caudal plexus and the veins are not so massive as 

 in various Armadillos ; nor is there any tendency to form 

 plexuses, such as are often met with in the Armadillos. In fact 

 the venous system of Orycteropus is in its entirety more 

 approaching that of other Eutherian Mammals. 



3. On Decapod Crustacea from Christmas Island, collected 

 by Dr. C. W. Andrews, F.R.S., F.Z.S. By W. T. 

 Calman, D.Sc, F.Z.S.t 



[Received May 22, 1909.] 



(Plate LXXII.J) 



I. Introductory. 



This paper deals with the Decapoda collected by Dr. Andrews 

 on his second visit to Christmas Island in 1908. The names of a 

 few specimens obtained during his stay on the island in 1897-98 

 but not hitherto determined are also included in the list given 

 below. 



Dr. Andrews has pointed out (P. Z. iS. 1900, p. 116) that " the^ 

 shores of Christmas Island ar-e singularly unfavoui-able for the 

 collection of marine animals," and practically all the marine 



* Am. Journ. Anat. vol. v. no. 2, 1906, p. 193, fig. 15. 



t Published by pei-missioii of the Trustees of the British Museum, 



X l!^or explauatiou of the Plate see p. 713. 



