DR BAIRD ON ENT0M08TRACA. 161 



Oenus ^th, — AcBOPEBUS — Baird. 



Somewhat harp-shaped, anterior margin terminating inferiorly 

 in a more or less blunt point projecting forwards ; inferior antennse 

 long. 



Sp. 1st. — A. harpse, Baird. Ann. Mag. Nat. Hist. 



Hab, Pond on Beaumont water at Yetholm. Dunglass pond, 

 &c. 



Sp. 2d. — A. nanus, Baird. Ann. Mag. Nat. Hist. 



Oenus 5th. — Alona — Baird. 



Shell quadrangular-shaped, striated ; inferior antennae short. 



Sp. Ist. — ^A. quadrangularis, Baird. Ann. Mag. Nat. Hist. 

 Lynceus quadrangularis, Muller. 



Hab. In the Pease bum, Cockbumspath : pool on Beaumont 

 water, Yetholm. 



Sp. 2d. — A. reticulata, Baird. Ann. Mag. Nat. Hist. 



Oenus 6th. — Pleuroxus— BatVd. 



Anterior margin prominent on upper portion ; the lower part 

 being truncated, or, as it were, cut sharp and straight. First pair 

 of feet very large. 



Sp. 1st. — ^P. trigonellus, Baird. Ann. Mag. Nat. Hist. Lyn- 

 ceus trigonellus, Muller. 



Hab. Pond at Fouldean, Berwickshire, and at Yetholm. 



Sp. 2d. — P. hamatus, Baird. Ann. Mag. Nat. Hist. Lyn- 

 ceus hamatus, Baird. Trans. Berw. Nat. Gub. 



Hab. Yetholm loch, and pool on Beaumont water, near Yet- 

 holm. 



Oentu 7th. — Pebacantha — Baird. 



Oval-shaped, lower extremity slightly curved backwards, and, 

 as well as the upper extremity of anterior margin, beset with 

 strong hooked spines. 



Sp. Ist. — P. tnmcata, Baird. Ann. Mag. Nat. Hist. Lyn- 

 ceus truncatus, Muller. Hab. Pool on Beaimiont water, near 

 Yetholm. 



SECTION 2.— OSTRACODA— Irair^Wtf. 



Body enclosed entirely in a covering of two valves, resembling 

 a bivalve shell, not divided into rings. Posterior jaws branchi- 

 fcrous. No external ovary. 



