1917-] S. Kemp : Notes on Crustacea Decapoda. 295 



A. Upper border of rostrum with 10 to 17 irregu- 



larly disposed teeth, forming at least three 

 distinct groups ; propodus of 3rd and 4th legs 

 expanded distally in males, the dilated portion 

 bearing numerous spines ... ... P. ciirvirostyis 



(Heller). 



B. L'pper border of rostrum with 19 to 32 teeth, 



forming an uninterrupted series ; 3rd and 4th 

 legs of male not modified. 



1. Carpus of ist peraeopods twice or more 



than twice as long as broad ; propodus 

 of 5th peraeopods less than four times 

 as long as dactylus ; dactyli of 3rd and 

 5th peiaeopods at least three times as 

 long as broad,' dactylus of 3rd per- 

 aeopod with 9 to 13 spines ... P. aiistraliensis, 



sp. nov. 



2. Carpus of 1st peraeopods less than twice 



as long as broad ; propodus of 5th per- 

 aeopods, at least in females, more than 

 four times as long as dactylus ; dactyli 

 of 3rd and 5th peraeopods less than 

 three times as long as broad ; dactylus 

 of 3rd peraeopod with 6 to 8, rarely 9 

 spines ... ... ... P. aiistniliensis, 



subsp. norfolk- 

 eiisis, now 



It is probable that the size of the eggs will afford a valuable 

 criterion in specific and subspecific differentiation ; but unfortu- 

 nately the collection contains ovigerous females only of P. curviros- 

 tris and of P. compressa subsp. improvisa. 



It will be noticed that in three of the five recognised forms 

 the third and fourth peraeopods of the male are modified, the 

 propodus being conspicuously dilated towards its distal end and 

 armed on the posterior margin of the expanded part with a great 

 number of short spines. Very similar sexual differences are met 

 with in Atyaephyra, a genus that has a circum-Mediterranean 

 distribution and is also one of the more primitive genera of the 

 family. In males of Atyaephyra desmaresti, as Barrois has shown,* 

 the third and fourth legs are modified on precisely the same lines 

 as in Paratya; but, strangely enough, the segment concerned is 

 not the propodus, but the merus. 



That sexual modifications of the third and fourth legs should 

 be entirely absent in the forms of Paratya from Australia and 

 Norfolk I. is very curious. Males are unfortunately scarce in 

 ray material from these localities and examination of further speci- 

 mens is therefore desirable. In no case, however, have I found 

 the slightest trace of modification, though the character is well 

 marked in much smaller specimens from Japan. 



Caiman* has noticed sexual differences in the length of the 

 spines on the third and fourth legs in Limnocaridina siimlis and L. 

 socius from Lake Tanganyika, while in other species of the same 



I Excluding all spines, both terminal and lateral. 



^ Barrois, Rev. Biol. Nord. France, V, p. 124, fig. 2 (1892). 



3 Caiman, Proc. Zool. Soc. London. 1906, p. 195. 



