148 TRICHOPTERYGIDZ. 
longest, the rest equal to each other in length. Legs generally short and very robust; tibie often 
strongly dilated; tarsi very short, setose, 3-jointed, with the basal joints often dilated; claws large and 
long ; posterior coxee faintly laminated. 
The species of this interesting genus, generally of rare occurrence, may be known 
from all other “ Ptiliina” by the base of their thorax overlapping the shoulders of the 
elytra. ‘They are very minute in size, which may in some measure account for their 
rarity ; and are divided into two very distinct groups, one containing those species which 
are smooth and shining and the other such as are clothed with dense pubescence. The 
Central-American species belongs to the latter group; it isa very elegant insect, covered 
with short silvery pubescence. 
The few known species inhabit Europe, North America, and New Zealand ; they are 
chiefly found on the sandy banks of streams and on the sea-coast. 
1. Actidium fowlerianum. 
Actidium fowlerianum, Matth. Cist. Ent. ili. p. 477; Trans. Am. Ent. Soc. xi. p. 146°. 
Elongatum, angustum, obscure castaneum, convexum, vix nitidum, pilis brevibus argenteis dense vestitum ; 
capite magno, obtuso, confertissime tuberculato ; oculis parvis, sat prominentibus ; pronoto parvo, transverso, 
quam caput nec longiore nec latiore, confertissime tuberculato, lateribus rotundatis et marginatis, ad basin 
sat abrupte contractis, margine basali rotundato ; elytris elongato-ovatis, sutura apicem versus elevata, late- 
ribus marginatis, apice angusto attenuato; pedibus flavis, antennis obscure flavis. Long. corp. lin.= 
0:37-0°50 millim. 
Head large, obtuse in front, closely covered with tubercles; eyes small, rather prominent; antenne moderate, 
rather robust, dusky yellow. Thora small, transverse, not longer or wider than the head, closely covered 
with tubercles, rather shining; the sides rounded, margined, and rather abruptly contracted at the base ; 
basal margin rounded. Scutellwm small, triangular, and acuminate. Hlytra elongate ovate, twice as long 
but scarcely wider than the head and thorax, closely asperate, with the suture slightly elevated poste- 
riorly ; sides margined, widest before the middle, and attenuated towards the apex ; apex rounded. Legs 
moderate, bright yellow. Underparts castaneous, with the mouth and coxe yellow. 
Hab. GuATEMALA, near the city (Champion! ?). 
Differs from the other species of the genus in its minute size, elongate and attenuated 
form, and close sculpture. 
Of this distinct and elegant insect some specimens ( ¢!) are much more attenuated 
towards the apex of the elytra than others. In an arrangement of the species of the 
genus it must be placed immediately before the New Zealand A. lineare, which it 
resembles more than any other yet discovered. 
Found on the banks of a stream in a “barranca” near the city of Guatemala 
(Champion). 
PTENIDIUM. 
Ptenidium, Erichson, Naturg. Ins. Deutsch. iii. p. 85 (1846) ; Matthews, Trich. Ilustr. p. 74, t. 6 
(1872). 
Body more or less ovate, very convex and shining. Head large, sessile, and prominent; eyes generally large 
and prominent. Thora small, transverse, commonly marked with four foves near the basal margin. 
Scutellum large, triangular. Llytra entire, ovate, generally rather long. Wings pedunculate, long and 
