CETJSTACEA. 301 



already given of it in the ' Catalogue of New-Zealand Crustacea' 

 will apply equally weU to the smaller Australian examples, except 

 that in these latter the eyes are distinct and dark-coloured, the 

 antero-lateral prolongations of the first thoracic segment (in the 

 smallest specimen especially) somewhat narrower at base, and the 

 posterior margin of the terminal postabdominal segment somewhat 

 arcuated*. 



The type of Pabricius's Gymoihoa imbricata is also in the British- 

 Museum collection (from the collection of Sir J. Banks), and I am 

 enabled to identify Leach's species with it with tolerable certainty. 

 The slight notch in the terminal segment mentioned by Fabricius is, 

 I think, merely due to an accident. As White referred Fabricius's 

 Gymoihoa imbricata to the genus Nerocila, and the type, when my 

 New-Zealand Catalogue was published, had not been placed in the 

 general collection of the Museum, I did not then suspect its identity 

 with C banksii. The species in the New-Zealand Catalogue (p. 107) 

 which I designated, after White, Nerodla imbricata must be called 

 Nerocila macleayii, White having previously used this name for it 

 (vide Dieffenb. Voy. New Zealand, ii. p. 268, 1843). 



It is not improbable that the original G. trigonocephala. Leach, 

 must also be regarded as synonymous with this species ; neverthe- 

 less, as the type specimens (which are dried and without definite 

 locality) present certain slight distinctive characters, as (e. g.) the 

 head is narrower, more distinctly triangulate, with straight sides, 

 and the anterior thoracic segment proportionately longer than is 

 usual in G. imbricata, I keep them provisionally distinct (c/. Ann. 

 & Mag. Nat. Hist. ser. 6, v. p. 463, 1880). To ascertain the true 

 distinctive characters of the species of this difficult group, a careful 

 revision of the whole subject is needed. Milne-Edwards's descrip- 

 tion of G. trigonocephala in the ' Histoire natureUe des Crustaces ' 

 seems to have been drawn up from specimens of a variety having a 

 more obtuse front, and the anterior margin of the first thoracic seg- 

 ment armed with a median lobe or tooth. Specimens presenting 

 these characters are in the British-Museum collection from Shark 

 Bay. Mr. HasweU, in his Catalogue, and Thomson {t. c.) merely 

 copy M.-Edwards's description. 



I refer specimens in the Museum collection to Geratothoa imhrir- 

 cata from Port Esaington {Haslar Hospital) ; Sydney, Murray Eiver 

 (A. E. Graven, from the mouth of a salmon-trout) ; Shark Bay, W. 

 Australia (from a species of Monaeanihus) ; Calcutta (designated by 

 White G. approximans) ; and various other specimens without special 

 indication of locality. 



3. Cirolana multidigitata, Dana. 



A small female from Albany Island belongs, I think, to this 

 species. 



* The posterior margin in I/eaeh's type is slightly rolled in through the desio- 

 cation of the specimen ; it should not have been described as "nearly straight." 



