392 REV. A. M. NORMAL AND ME. G. S. BEADY 



carapace, but the infero-anteal portion of the valves (i.e., the 

 portion which covers the feet) is sculptured with arched striae, 

 as represented in the figures of Jurine and Schoedler. Head 

 not hooded, produced into a long acute rostrum, which is bent 

 downwards ; anterior antennae considerably shorter than the ros- 

 trum; posterior antenna? short. Eye of moderate dimensions, 

 eye-spot fully half its size, situated about midway between the 

 eye and the extremity of the rostrum, rather nearer the former. 

 Abdomen short, rather broad, somewhat narrowed at the extre- 

 mity, where it is broadly truncate, sinus anterior to the marginal 

 spines slight, marginal spines very minute, subequal in size ; 

 claws slender, curved, having a delicate spine springing from 

 near the base. Length, iVth of an inch. 



The form of the carapace is not unlike that of the last-de- 

 scribed species,- but independently of the difference in surface 

 sculpture of the carapace, and the position and size of eye-spot, 

 &c, a glance at the abdomen, which is very distinct in the two 

 species, at once suffices to distinguish them. As compared with 

 L. IcBvis, moreover, the carapace of P. trigonellus is very much 

 wider in front. At "Hell Kettles," and Crag Lake, the two 

 species are found in company. 



This species appears to range throughout the whole of Europe, 

 having been observed at Geneva, in Russia, Prussia, Norway, 

 Sweden, and the British Islands. In our own country it appears 

 to be a local species, though generally distributed, having been 

 found by Dr. Baird in several places around London, in a pond 

 at Fouldean, Berwickshire, and at Yetholm, Roxburghshire ; by 

 A. M. N. in Hardwicke Lake and the Forge Dam, near Sedge- 

 field, county of Durham, in Crag Lough, and Holy Island Lough, 

 Northumberland; by G. S. B. at "Hell Kettles," county of 

 Durham, and Lochmaben, Dumfriesshire ; and by Mr. D. Robert- 

 son in the Paisley Canal, near Glasgow. It delights in clear 

 water. 



The Pleuroxus hamatus of Baird, with its hook-formed feet for 

 clasping the female, is (as was suggested might be the case by 

 Dr. Baird himself in a foot note) the male of his Pleuroxus 

 trigonellus. 



