114 HYDROPHILIDA. 
testaceis; capite thoraceque dense subtilissime aciculato-strigosulis ; elytris striatis, striis internis subtili- 
oribus, externis remote crenatis; pectore abdomineque basi sat fortiter punctatis. 
Long. §, lat. 4 lin. 
Hab. GUATEMALA, Cubilguitz (Champion) ; Nicaraeua, Chontales (Janson). 
The narrow oval form attenuated behind, and the excessively convex upper surface, 
combined with the peculiar sculpture of the head and the thorax, make this species 
easily recognized. The pubescence of the upper surface is very scanty and fine, and so 
is not readily noticed. The apical portion of the elytra is usually somewhat paler, as 
in many other of the allied species. The front tibiz are slender and without any trace 
of emargination ; and their outer margin bears only exceedingly minute spines, while 
the middle and hind tibie are quite unarmed. Owing to the very convex and peculiar 
form, the length of the prothorax is about twice as great along the middle as it is at: 
the lateral margin. 
DELTOSTETHUS. 
Corpus convexum, latum, elytris sulcatis. Mentum magnum, basi parum prominula. Palpi maxillares graciles, 
parum elongati, articulo secundo basi tenui, apice incrassato. Coxe anteriores haud contigue. Proster- 
num in medio elevatum sed haud planum, carinatum, posterius emarginatum. Coxe intermedie sat 
distantes. Mesosternum in medio pentagonum elongatum formans, pentagoni angulis parum discretis. 
Tibiew fere espinulose. 
This genus should be placed between QOosternum and Cryptopleurum. It differs 
from the former in numerous points of structure, of which the most important and 
easily observed is the shape of the central piece of the mesosternum: this forms a large, 
flat, but strongly margined tablet in front of the middle coxe; this pentagon is quite 
as long as, or longer than broad, and its lateral angles are but little marked, so that it 
approximates in form to a broad oval. From Cryptopleurum the genus is very distinct 
by the less widely separated middle coxe and the different shape of the mesosternal 
tablet, by the structure of the middle of the prosternum, which, though very distinctly 
differentiated from the lateral parts, is not flat and is strongly carinated along the 
middle; the margins of the prothorax, too, form sharp edges and are not inflexed. 
I am not acquainted with any species of the genus other than the two discovered by 
Mr. Champion. 
1. Deltostethus sulcatus. (Tab. IV. fig. 2.) 
Rotundato-ovalis, posterius acuminatus, niger, subtus picescens vel rufescens; capite thoraceque crebre, pro- 
funde punctatis, opacis vel parum nitidis; elytris nitidis, profunde sulcatis, sulcis crenatis, interstitiis haud 
punctatis, vix pubescentibus; antennarum basi, palpis pedibusque testaceis. 
Long. 1, lat. vix 2 lin. 
Hab. GuateMALA, Purula, Senahu, San Juan in Vera Paz, Capetillo, Las Mercedes 
3000 feet (Champion); Panama, Volcan de Chiriqui 2000 to 3000 feet (Champion). 
The species varies much in colour, being sometimes very black, becoming in other 
specimens more dilute, and when rather immature is sordid yellow; the mentum is 
