OHCnESTID.K. 17 



4. ORCHESTIA, Uach. 



This genus, founded by Dr. lA'uch, is separated from the last by 

 a \evy slight luvtural distinction. The fii'st pair of gnathopoda possess 

 a subcheliforra character in Orchestia, whilst in Talitnis ami Or- 

 chtstoiih'ci they are simple. The connexion is cb'awn still closer by 

 the intermediate fonn, Talorchestia, in which the females possess the 

 generic features of TaJitrus, Mhile the males retain those of Or- 

 chestia. The two verv ihstinct genera of Orchestia and TaJitrus ai-e 

 but the opi)osite extremities of the same natural group. 



The antennse resemble those of the three preceding genera; but 

 we have not detected a sexual variation, as in 2\ih'fnis Locusta. 



The rirst paii- of gnathopoda exhibit the generic separation fi'om 

 Talitrus ; they possess a subehelifoiTn character, alike in form in 

 both sexes, and do not appear to be very important organs. 



The whole aninud is more compressed than Talitrus, and is most 

 commonly found of a dull greenish coloiu*. 



1. Orchestia AucklandiaB, n. s. (Plate I. a. fig. 3.) 



Male. — Eyes very small, round. Superior antenna? reaching to the 

 extremity of the penultimate joint of the peduncle of the inferior. 

 Inferior antenna; nearly one-third the length of the animal. First 

 pair of g-nathopoda having the caqms longer than the propodos, 

 with a tubercle on the inferior margin ; the palm produced into a 

 rounded tubercle. Second paii' of gnathopoda broader at the palm 

 than at the cai-pus ; palm slightly oblique, the inferior half raised 

 higher than the half nearest the base of the dactylos, and fringed 

 ^vith short, equidistant, solitaiy hairs ; a notch near the inferior 

 angle separates a tooth from the rest of the palm ; dactylos exca- 

 vated near the base. 



Female. — The fii-st pair of gnathopoda differ from those of the male 

 in being longer and slighter ; the second pair of gnathopoda in 

 having the cai-pus longer than the propodos, and not interiorly 

 tuberculated. The animal is generally very smooth, clean, and free 

 from hairs. 



Length rather more than an inch. 



Hah. Auckland. 



The s])('(imen from which the species is descri1)ed was procured 

 during the Ex])edition of the Astrolabe, and, with many others, 

 was kindly entnisted to me for examination by M. Milne-Edwards. 

 It is presci-ved in the Museum of the Jardrn des Plantes at Paris. 



2. Orchestia Fuegensis, n. s. (Plaxj: I. a. fig. 2.) 

 Male. — Eyes very small, round. Supeiior antenmc nearly as long 

 as the peduncle of the inferior. Inferior antenna) not one-fourth 



c 



