1906.] CRUSTACEA OF THE THIRD TANGANYIKA EXPEDITION. 201 



last thoi^acic somite and that the epipods extend to the third 

 perfeopods. On these grounds I refer it provisionally to the 

 genus Caridella. Fi-om the preceding species it is distinguished 

 by the characters of the first perseopods and the well-armed dactyli 

 of the third and fourth. 



Occurrence. — Near mouth of Lofu, 6.x. 04. " Taken on rocks, 

 shallow water. Colour yellowish, with red spots ; eggs green." 

 One specimen, ovigerous. 



Karema, 12.xii.04. " Tow-netting, surface, 8.30 p.m." Six 

 immature specimens. 



Genus Atyella, gen. nov. 



Perseopods -without exopods ; carpus of first and second pairs 

 excavated distally ; chelfe without any distinct palmar portion. 

 Epipods on the first three pairs of perseopods. No pleurobranchia 

 on the last thoracic somite. 



Type, A. hrevirostris^ sp. n. 



This genus bears the same relation to Caridella tYiiit Atya bears 

 to Caridina, differing in having the carpus of the second perseopods 

 excavated and the palmar portion of the chelae obsolete. Perhaps 

 the comparison should be with Ortmannia {Atyoida) rather than 

 with Atya, for the two fingers of the chelae, the propodus and 

 the dactylus, are not exactly alike, though the articulation 

 between them is pi-actically in a straight line with their opposed 

 edges. In any case, the new genus is distinguished from both of 

 those just mentioned by the reduced number of the branchiae. 

 In Ortmannia 2)otimirivi, the' only species, so far as I know, which 

 resembles the present genus in having no epipods on the penul- 

 timate pair of legs, Fritz Miiller states that there are seven gills 

 on each side, one above each of the five thoracic legs, one above 

 the external maxilliped, and a very small one on the second 

 maxilliped (Arch. Mus. Rio de Janeiro, viii. p. 166, 1892). The 

 branchial formula for Atyella is the same as that given above for 

 Caridella. 



Referring to a bottle containing both the species described 

 below, Dr. Cunnington notes that the specimens were "red in the 

 dark, changing to light violet in the light ; with red-brown setse 

 on the chelae." Fritz Miiller has described changes of colour 

 in Ortmannia (Atyoida) j^otimirim (t. c. p. 155, also Kosmos 

 (Stuttgart), Jalii^g. iv. Bd. \'iii. p. 472, 1881). 



Atyella brevirostris, sp. n. (Plate XIV. figs. 57-64.) 



Description. — Rostrum (Plate XIY. fig. 57) generally less than 

 one-third of length of carapace, reaching just beyond end of first 

 segment of antennular peduncle or neai'ly to end of second, 

 slightly decurved, teeth ^_^ -, those on upper edge extending* 

 nearly to tip. Antennular peduncle (Plate XIY. fig. 58) a little 

 shorter than antennal scale ; first segment equal to second and 

 third together, external spine of first not reaching end of segment 



