198 Transactions. — Zoology. 



the same forms have been described by several different 

 authors under a great many names. By the pubhcation of 

 his monograph on the Gammarini of the Gulf of Naples in 

 1893 Delia Valle has done excellent service in bringing 

 together in the systematic part of his work the scattered 

 references to these species. I have myself erred not only in 

 the creation of unnecessary new species, but also in wrongly 

 referring my specimens to already existing species, although 

 in the latter case the error was chiefly due to inadequate 

 diagnosis in the first instance. While agreeing with most of 

 Delia Valle' s work, I find that he has himself fallen into some 

 errors in the opposite directions — errors which, perhaps, were 

 not easily to be avoided by him. Thus two species may be 

 morphologically so alike that it may seem desirable to the 

 systematist — working only from laboratory specimens — to 

 unite them, while the habitat and mode of life of the two 

 forms may be so distinct that we have reason to believe that 

 they are good physiological species. As a case in point, this 

 has been done by Delia Valle in uniting Orchestia tumida to 

 0. gammarellus. There are considerable morphological differ- 

 ences between the two forms, but it is in their habitat and 

 mode of life that they show the most marked dissimilarity. 



It is a difficult matter to select any features sufficiently 

 distinctive upon which to found specific diagnosis; hence it 

 becomes a matter both useless and rather misleading to base 

 questions of geographical distribution on such species. After a 

 superficial examination of some thousands, and the dissection 

 and drawing of some hundreds of specimens, I have reduced 

 the number of New Zealand species of Orchestia to seven, 

 exclusive of the doubtful 0. serrulata of Dana. The specimens 

 I formerly referred to this species prove to belong to 0. 

 gammarellus, and I am doubtful now whether Dana's is a 

 valid species. Among all my large collections, made from 

 many parts of these Islands, I cannot find any which will 

 answer to it. On the other hand, Dana's description will suit 

 either 0. gammarellus or 0. telluris, while his figures are not 

 sufficiently detailed to be of much value in classification. 



The following are the forms which are represented in New 

 Zealand : Orchestia, 7 species ; Hyale, 4 species ; Hyalella, 

 1 species ; and Ceina, 1 species : — 



Genus 1. Orchestia, Leach. 

 1. Orchestia gammarellus, Pallas. 



(The full synonymy of this ubiquitous species is given by 

 Delia Valle, pp. 499-501, but the New Zealand and Aus- 

 tralian references, which have been personally verified, 

 are given herewith.) 



