984 On Aquutic Corjiirorous Coleoptera or DijtisciiUn. 



Fig. 18. Pi-ostPi-nal process of C:mtliy(lni-;, (C. gniininicus). 



Fig. 19. Prosternal pi-ocoss of Hyclrovatus. 



Fig. 20. Prosternal process of Platj-nectes. 



Fig. 21. Prosternal process of Neptostenius. 



Fig. 22. Prostenial process of LaccopLilus (D}tiscus maculosus, Geim.) 



Fig. 23. Mesostcnmin of Dytiscus (D. niargiiialis, L.) ; a, episteruum ; b, epimeron ; c, portion of margin 

 of iniiliUe coxal caA'ity ; '/, iiiedisternum. 



Fig. 2-t. Mesostcrnum of Hyilroeantluis (H. atripennis), one side removed ; lettering as in fig. 23. 



Fi". 25. Middle coxal cavity looked into, and seen laterally, of Eretes ; a, mesosternum ; h, metaster- 

 num ; c, vacant space forming a foramen of comnumication with tlie cavity of otlier side of 

 body. 



Fig. 2G. Same parts in Hydaticus rimosus. 



Fig. 27. Same parts in Dei-onectcs (DytLscus assimilis, Payk.) 



Fig. 28. Same pai-ts in Deronectes (Hydroporus luctuosus, Aube). 



Fig. 29. Same parts in Hvdroportis (Hypliydrus memnonius, Nic.) 



Fig. 30. Diagram of pieces surrouudinj; middle coxal cavity in Hydrocantlius (Dytisci fragmentali) ; 

 a, mesosternum (medisternuin) ; h, its cpisternnm ; c, its epimeron ; d, episternnm of meta- 

 sternum, with exposed and thickened anterior margin simulating an additional piece ; e. 

 metastemum ; f, coxal cavity. 



Fig. 31. Similar diagram of Laccophilus (also Dytisci fragmenti). 



Fig. 32. Similar diagram of Colymbetes (Dytisci comj)licati), but with epipleura represented ; a, meso- 

 sternum ; h, its episteruum ; c, epijileura ; (/, metathoracic episternnm with incrassate and 

 exposed anterior liortler; e, inetasternum ; f, coxal cavity; g, mesothoracic epimeron. 



Fig. 33. Diagram of the middle of undersurface in Silphomorpha (Carabidoe, Pseudomorphini) ; a, meso- 

 sternum [)roper (medisternum) ; h, its e]usternum ; c, its ejiimeron ; d, metasternum ; e, its 

 episteinum ; f, its epimeron ; (j, internal lamina of hind coxa ; /(, external lamina of hind 

 coxa ; i, first ventral segment ; /•, middle coxal cavity. 



Fig. 3-1. Diagram of same parts in Procrustes (Carabida?, Carabini) ; in tliis the parts of the side pieces 

 usually covered by the wingcases are introduced ; and f, indicates the external portion of 

 the metathoracic episternum to which the membranous epimeron is attached, the suture 

 between these two pieces being really placed on the inner face of tlie episternum and thus 

 concealed : otherwise lettei'ing as in fig. 33. 



Fig. 35, Diagram of same parts in Cybister (Dytiscus rceselii) ; the lateral portions are covered by the 

 wingcase when this is closed ; letterii^g as in fig. 33. 



Fig. 36. Metasternum and hind coxa; of Ampliizoa. 



Fig. 37. Idem „ Pelobius. 



Fig. 38. Idem „ Suphis. 



Fig. 39. Idem „ Noterus. 



Fig. 40. Idem „ Hydrovatus. 



Fig. 41. Idem „ Queda. 



Fig. 42. Idem „ Laccophilus. 



Fig. 43. Idem „ Hyphydrus, on the right side of this figure, the first ventral 



segment, and the external parts [of the pieces usually concealed by the wingcase are 

 introduced. 



Fig. 44. Metasternum and hind coxa; of Methles. 



Fig. 46. One side of metastemum'and hind coxa of Coelambus. 



Fig. 46. Hind coxa of Hydroporrs. 



Fi;;. 47. Idtfii of Paroster. 



