206 THE VOYAGE OF H.M.S. CHALLENGEK. 



Observations. — This specimen appears very closely to resemble Astacus australasi- 

 ensis, Milne-Edwards, recorded from New Holland, 1 from which it appears to differ in 

 several details, the most distinguishable being that it has three small teeth on each 

 side of the rostrum instead of one, that it has two teeth longitudinally situated on the 

 carapace on each side behind the orbit instead of being smooth, and one tooth instead 

 of three on the inner margin of the carpos of the first pair of pereiopoda, and that the 

 inner margin of the propodos is less strongly serrate. 



The inner margin of the second pair of gnathopoda is serrate, while the drawing of 

 the part shown in Milne-Edwards' figure represents it as perfectly smooth. 



Milne-Edwards' description is stated to be taken from a young animal. Ours is from 

 a female, but whether fully grown or not there is no means of determining. The vulva 

 appears to be imperforate, but whether this be due to the immature condition of the 

 ovaries, or, as I am inclined to believe, from a recurring state of biannual rest, we 

 are not at present able to determine. I have observed the calcified condition of the 

 vulva in numerous instances where there was clear evidence of adolescence, a circumstance 

 that induces me to believe in the probable correctness of the opinion that these animals 

 may breed only every other year. 



Tribe Stenopidea. 



Anterior margin of the carapace produced to a laterally compressed rostrum. 

 Anterior three pair of pereiopoda chelate, of which the posterior pair is the longest 

 and largest. 



Branchige filamentous. 



Brephalos. a Megalopa or a Zoea. 



In this tribe there is but a single family. 



Family Stenopid^e. 



Podobranchial plume absent from all excepting the first pair of gnathopoda. Posterior 

 pleurobranchial plume the largest. Basecphysis of the second pair of gnathopoda small, 

 slender, and almost rudimentary. 



The two genera that are here grouped together in this family have by all preceding 

 carcinologists, including Mdne-Edwards, de Haan, and Dana, been placed in the family 

 of the Penseidse. 



This was done, it appears to me, on the external evidence that Penasus has, in common 

 with Stenopus and Spongicola, the anterior three pairs of pereiopoda developed in the 



1 Hist. Nat. Crust., vol. ii. p. 332, pi. xxiv. figs. 1-5. 



