CLASS V. IX SECT A. 187 



Genus 148. IIYDROBIUS. Leach. 

 Body oval, convex, obtuse : ej/cs simple. 



* Elytra striated. 

 Sp. 1. Hydr.fuxcipes. 

 Inhabits ponds. 



** Elytra smooth. 

 Sp. 1. Hydr. melunoccphahis. 

 Inhabits ponds. 



B. Elytra with tlic apex truncated.- Scutcllum small. 

 Genus 149. LIMNEBIUS. Leach. 

 Body rather depressed : eyes simple. 



Sp. 1. Lim. nitidus. Ilydropliiliis nitidus. Marsh, 

 Inhabits ponds and ditches. 



STira'S 3. — Clypcus whole: sternum produced into a spine. 



Genus 150. HYDROUS. Linnts MSS., Leach. 

 Scutcllutn large : anterior tarsi of the male dilated in the middle with UH' 



equal claws: antennce w'ldi their last joint acuminated. 

 Sp. 1. Hydr. piceus of nuthoTS. 

 Inhabits ponds and ditches. 



Genus 151. HYDROPIIILUS of authors. 

 Body with the posterior part slightly obtvise: antenna: with the last 

 joint obtuse : scutellum moderate : anterior tarsi in both sexes simple. 

 Sp. 1 Hydr. caraboidcs of authors. {Bl. 3. fg. 16.) 

 Inhabits ponds ; is very common. 



Fam. XXI. Sph.i;ridiad.5:. Leach. 



Antenna terminated by a club : maxillary palpi very long : mentum large, 

 clypeiform: headw'iXh the front rounded, cowl-shaped: feet formed 

 for walking : tarsi with the basal joint as long or longer than the 

 second joint (in the male with the last joint on the anterior tarsi 

 large). The insects of this family are very nearly akin to the Hy- 

 drolophii. 



Genus 152. SPH.^RIDIUM. Fahr., Oliv., Lamarck, Leach. Der- 



MESTES. Linn., De Geer, Marsh. 



Body somewhat hemispheric : eyes immersed : thorax transverse : tibitr 



spinose, armed with heels : sternum behind produced into a conic 



spine. 



Sp. 1. Sph. scarabccoides. Black, shining, smooth : scutellum forming a 



long triangle : feet very spiny : each elytron at the base with a blood- 



