704 THE VOYAGE OF H.M.S. CHALLENGER. 



But since appendages which are more or less peculiar in feature in the adult stage pass 

 through forms of less normal character, I was strongly inclined to believe that Caridina 

 was only a young stage of Atya. The locality of Milne-Edwards' Caridina typus is 

 unknown, and it is not said whether it was found in fresh or salt water. Its association 

 with the genus Atya from the Cape Verde Islands is significant, and its juvenile condi- 

 tion is suggestive of a relationship that can only be determined by a demonstration of the 

 adult form of Caridina, or by more complete knowledge of the development of Atya. 



Geographical Distribution. — Our specimen of Caridina typus was taken at San 

 Iago, Cape Verde Islands, associated with Atya sulcatipes and Atya (Atyoida) serrata. 

 It was probably here that Milne-Edwards' typical specimen was obtained. Caridina 

 longirostris is stated by Milne-Edwards to have been found b) r Boux in the riviere de la 

 Macta, near Oram Stimpson records Caridina grandirostris, Caridina brevirostris, and 

 Caridina exilirostris from the Island of Loo-Choo ; Caridina leucostica from a river 

 near the town of Simoda in Japan ; Caridina multidentata and Caridina acuminata 

 from the mountain streams in the island of Bonin, and Caridina serrata from rivulets in 

 the Island of Hong Kong. Caridina nilotica, Boux, is recorded from Mozambique by 

 Hilgendorf. 1 



Caridina typus, Milne-Edwards (PL CXIX. fig. 3). 



Caridina typus, Milne-Edwards, Hist. Nat. Crust., torn. ii. p. 363, pi. xxv. bis, figs. 4, 5. 



" Bostrum sharp pointed, straight, of moderate proportion, not reaching the 

 extremity of the second joint of the first pair of antenna?, and armed on the under 

 surface with three little teeth. First pair of pereiopoda not so long as the second pair 

 of gnathopoda. Extremity of the chela fringed with numerous hairs. 



" Length about 10 lines. 



" Habitat ? " 



Such is the account Milne-Edwards gives of a small animal similar to that obtained 

 by the Challenger from a rivulet in the valley of San Antonio, San Iago, Cape Verde 

 Islands, and which corresponds closely with his description and illustration in every 

 detail, excepting that in our damaged specimen the first pair of pereiopoda is longer 

 than the second pair of gnathopoda. In our specimen the pereion is preserved, 

 including all the appendages, from the mandibles to the posterior pair of pereiopoda, 

 but separated from the carapace and pleon, which were also found in the same bottle. 



The mandibles and the other oral appendages, so far as they have been observed, 

 correspond in form with those of Atya, which is found in the same locality. 



The second pair of gnathopoda has the terminal joint shorter than the penultimate, 



1 Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 838, 1878. 



