DYTISCIDiE. 
Ins. 37 
discontinuous. To include Vatellus haagi , Wehncke ; V. grandis , Buq., 
and M. lateralis (pi. ix. fig. 116), Uruguay, rudis , S. America, sahlbergi, 
Petropolis, p. 283, marginalia, S. America (Santa Rita) mexicanus , 
Mexico \cf. also Biol. Centr. Am. Col. i. (2) p. 8], p. 284, and ventralis , 
Brazil, p. 285, spp. nn. 
Derovatellus, id. 1. c. pp. 286 & 841. Allied to Vatellus , size small ; 
mesosternum not much exposed ; ventral sutures ordinary. Type, V. 
lentus , Wehncke, figured, pi. x. fig. 118. 
Neptosternus , id. 1. c. pp. 317 & 843. Allied to Laccophilus ; prosternal 
process acutely tridentate ; spurs of hind tibiae acuminate at apex, head 
rather short, hinder angles of prothorax very acute. Type, A. ornatus , 
sp. n., 1. c., Zanzibar, Madagascar (figured as N. Widens, pi. x. fig. 120). 
Queda , id. 1. c. pp. 336 & 849. Allied to Hydrovatus , coxal incision 
shorter in the longitudinal than in the transverse direction ; only the 
fringes of the labrum visible. Type, Q. compressa , sp. n., 1. c. pi. x. 
fig. 122, Santa Rita, Brazil. 
Ueterhydrus , id. 1. c. pp. 337 & 850. Allied to Hyphydrus ; labrum 
conspicuously exserted on under surface of head ; middle coxa) rather 
widely separated ; prosternal process broader than long, its obtuse hind 
margin reaching the metasternum. Hind tibiae straight, the basal por- 
tion not conspicuously narrower than the apical one. Type, Hyphydrus 
senegalensis , Aube (figured, pi. x. fig. 124). 
Pachydrus , id. 1. c. pp. 338 & 850. Allied to Hyphydrus ; labrum con- 
cealed, only its front margin and fringes being visible ; middle coxae 
rather widely separated ; prosternal process broader than long, its obtuse 
hind margin reaching the metasternum ; hind tibiae straight, their basal 
portion not conspicuously uarrower than the apical one. To include 
Hyphydrus ohniger , Chevr., probably H. cayennensis, Cast., and globosus , 
Aube, and P. punctatus , pi. x. fig. 125, Brazil, cribratus , Mexico, Guade- 
loupe, p. 338, obesus , Venezuela, and brevis , Porto Rico, Antigua, p. 339, 
spp. nn. ; add P. politus , sp. n., id. Biol. Centr. Am. Col. i. (2) p. 16, Gua- 
temala, Mexico. 
Bidessus , id. Tr. Dubl. Soc. (2) ii. pp. 344 & 852. Allied to Hyphydrus, 
prosternal process longer than broad, parallel-sided, but with a more or loss 
acute extremity which attains the metasternum ; intercostal process of 
metasternum not attaining the metasternal fork, so that when the prothorax 
is taken away, it may be seen that the middle coxaa touch one another ; 
posterior tibiae with the basal portion much more slender than the apical 
one ; coxal lines longer than prosternal process. Upwards of 80 species, 
occurring in all parts of the world, are referred to this genus, those pre- 
viously known were mostly described under Hydroporus ; the following 
are new : — B. migrator , Australia, p. 345, borrii, Pernambuco (P), p. 346, 
bicristatus, Jeddah, dohrni (Wehncke, MS.), S. W. Africa, p. 347, insignis, 
pi. x. fig. 128, Hedjaz, pictodes, N. America, p. 348, obesus , Texas, p. 349, 
discretus , Texas, p. 350, coxalis , Madrid, Tangiers, p. 351, major, Arabia, 
Persia, Iceticulus , Siam, Macassar, p. 354, strigicollis (Fairmaire, MS.), 
Madagascar, sordidus , Abyssinia, p. 355, striola, Celebes, signatus, godef- 
froyi (Wehncke, MS.), p. 356, dcemeli (Wehncke, MS.), Australia, 
orthogrammus, N.W. Australia, p. 357, transversus, p. 358, fuscipennis, 
