44 MANDIBULATA. — COLEOPTERA. 



■what globose ; the following, to the tenth, nearly equal in length, elongate, 

 clavate: the terminal elongate acute; head ovate; eyes very prominent: 

 thorax bisinuate behind : scutellum exposed, triangular : body oval, convex, 

 obtuse posteriorly : legs gressorial, the hinder femora free : claws didactyle. 

 Males with the four anterior tarsi equally dilated. 



Pselobius differs from Haliplus and the five following genera by 

 having a distinct, exposed, scutellum, and from the remaining Dy- 

 ticidse by having all the legs gressorial : it also differs in other im- 

 portant characters, as above pointed out, and very conspicuously by 

 the great convexity of its body, which somewhat approaches to the 

 form of that of the genera Haliplus, Hyphidrus, and Hygrotus. 



Sp. 1. Hermanni. Ferrugineus, oculorum ambitu, margine antico et postico 

 thoracis, elytrorumque disco nigris. (Long. corp. 5 — 5^ lin.) 



Dy. Hermanni. Linne.—Don. xiv.pl. 501. f. 2. — Pae. Hermanni. Steph. Catal 

 p. 43. No. 425. 



Ferruginous : head with a black patch round the eyes, expanded towards and 

 somewhat approximating on the forehead : thorax with its anterior and pos- 

 terior margins black: elytra with a large black patch on the disc, the 

 anterior and lateral edges a little sinuated with the ferruginous ground, very 

 convex, rugose, with several smooth longitudinal lines, which converge to- 

 wards the suture at the apex : abdomen with the base ferruginous, the apex 

 black ; breast and sides of the thorax the same : legs pale ferruginous. 



Pae. Hermanni is not a very abundant insect, especially in the 

 northern counties, where, I believe, it occurs but rarely, if at all : 

 near the metropolis, however, I have met with it in several places, 

 particularly in the ponds in Copenhagen-fields : it occurs in Norfolk. 

 When taken it makes a noise by the friction of its abdomen against 

 the elytra. " Once found in a stream close to Cambridge." — Rev. 

 L. Jenyns. " Wandsworth-common, Hampstead-heath, and Sun- 

 bridge, in Kent." — Mr. Ingpen. " Ditches and ponds near Lime- 

 house and Bow." — Mr. Stone. 



Genus LXXIX. — Hyphidrus, Illiger. 



Palpi, external maxillary with the terminal joint elongate conic, the preceding 

 short cylindric : labrum transverse entire : mandibles emarginate at the apex : 

 mentum anteriorly emarginate, the centre scarcely produced. Antenna very 

 short, the two basal joints largest, the fourth smallest, the terminal longest, 

 abruptly acuminate : head rounded, depressed : thorax very short, transverse, 

 produced in the middle behind : scutellum none : body nearly globose : legs 

 formed for swimming: the four anterior tarsi four-jointed, with the last 

 joint abbreviated; the posterior tarsi with one claw. 



