326 Zoological Society. 



This species is of an olive-green hue, and is smaller than the Apus 

 eancriformis. The carapace is of an oval form and covers more 

 than two-thirds of the body. The notch at its posterior part is less 

 deeply lunated than in Apua eancriformis, and the keel which runs 

 down its centre is well-marked. The flap of the caudal segment is 

 of an elongated oval shape and has a keel running down its centre, 

 which, as well as its edges, are finely serrated, or beset with nume- 

 rous short setee. The tail-setse are also furnished on each side with 

 numerous short hairs, which, when magnified, present a fine plu- 

 mose appearance. The first pair of feet or rami are very small, and 

 when the animal lies prone are indistinctly visible. 



2. Lepidurus glacialis, Kroyer. Clypeo corporis tres partes 

 tegente, rotundato, viridi ; setis caudce plumosis ; lamina cau- 

 dali abbreviata, subquadrata, denticulata. 



Long, toti corporis 1 poll. ; lat. clypei 'b poll. 



Apus glacialis, Kroyer, Voy. en Scandinavie, Lapponie, &c. t. 40. 

 f. 1. 



Hab. In America boreali ; detecta ad " Cape Krusenstern " mense 

 Augusti 1849. Collegit Dominus J. Rae. Museum Britannicum. 



This species is smaller than the preceding, and of a green colour, 

 having the carapace of a rounded form with a sharp keel running 

 down the centre. It covers rather more than two-thirds of the body, 

 and has the notch at its posterior extremity small and finely toothed 

 on its edges. The spines on the body are small and of the same 

 colour as the body itself. The first pair of feet or rami are very 

 short, scarcely visible when the animal is in a prone position beyond 

 the edge of the carapace. The tail-setse are finely plumose, and the 

 flap between them is of a somewhat square shape, short and toothed 

 on its edges. 



3. Lepidxjrtjs virtdis, Baird. Clypeo corporis magis quam di- 

 midiam partem tegente, rotimdato-ovali, viridi, valide carinata ; 

 setis caudce brevi-pilosis ; lamina caudali ovali-lanceolata, cari- 

 nata, denticulata. 



Long, toti corporis 2 poll. ; lat. clypei 1 poll. 



Lepidurus viridis, Baird, Proceedings of Zool. Soc. 1850, t. 17. f. 1. 



Hah. "Van Diemen's Land." Museum Britannicum. 



This species resembles considerably the Lepidxirus prodnctus. It 

 is two inches long, and has the tail-setse nearly as long as the body. 

 The carapace and whole body are of a fiue green colour ; the cara- 

 pace of a rounded oval form and covering about two-thirds of the 

 body. The edges of the notch in the posterior part of the carapace 

 ar€ strongly toothed, and those of the inferior half of the carapace 

 are very finely serrated. The keel running down the centre is well 

 marked and projects a short way beyond the edge of the notch. The 

 tail-setse are beset with very numerous short hairs, and the flap be- 

 tween them is of an oval lanceolate form, and has the keel beset 

 with short sharp spines and the edges finely serrated. The first pair 

 of feet or rami only slightly extend beyond the edge of the carapace. 



