Entomological Society. 8981 
ample in P. porcicollis, and the coarse punctures in the transverse sulci are more nu- 
merous and more evident, especially on the hinder part of the the thorax, behind the 
posterior transverse ridge: the elytra are more strongly sulcated, and the punctures in 
the sulci are larger, and separated from each other, for the most part, only by narrow 
transverse ridges; the interstices of the strie are broader; and lastly, the outermost 
interstice is continued from the base of the elytron only about half-way towards the 
apex, so that the two outermost strie become confluent beyond that part. The corre- 
sponding interstice in P. sulcicollis is at first (near the humeral angle of the elytron) 
united for a short distance with the much more prominent interstice which is nearest 
to it, and then is free, and extends to the apex of the elytron. 
“ Onthophilus exaratus, De Marseul, Essai Monographique sur la Famille des His- 
térides, Ann, de la Soc. Ent. de France, 3me sévie, iv. p. 552, sp. 2. | Hister exaratus, 
Tilig. Magaz. vi. 48, 25 (1807).— The insect exhibited is as large as the largest speci- 
mens of QO. sulcatus, and is placed by De Marseul and others in the section of the 
genus in which there is an odd number of longitudinal ridges (5) on the dorsal surface 
of the thorax,—a section which includes our O. sulcatus; whilst our common smaller 
species, O, striatus, is placed in the section having an even number (6) of ridges on 
the thorax. Of course in the former case there would be a mesial ridge, and the spe- 
cies of the second section would be destitute of a mesial ridge, and thus two distinct 
types of sculpturing might be said to exist in these very closely-allied insects,—a pe- 
culiarity which would not be in accordance with our general experience. The O. exa- 
Tatus, however, shows that such is not the case. All the species have six ridges. The 
differences in the three species are, that in O. striatus the four ridges on the dorsal 
surface of the thorax are equidistant and entire, and they extend frow the base to the 
apex of the thorax ; the other two ridges are short, confined to the hinder half of the 
thorax, and situated, one on each side, rather nearer to the lateral margin than to the 
dorsal ridges. In the other two species the above so-called four dorsal ridges are 
interrupted, the outer pair vanishing on the anterior third of the thorax, and the 
middle pair interrupted about midway between the base and apex uf the thorax, and 
reappearing, more widely separated, on the fore part. In O. sulcatus the two middle 
ridges are almost united into one ridge, being separated only by a slender impressed 
line. In O. exaratus the two corresponding ridges are distinctly separated by a shal- 
low, densely punctured groove ; the space between them and the nearest adjoining 
ridge on either side is, however, fully three times greater than that which separates 
the middle pair. ©. sulcatus has the abbreviated outermost ridge on either side well 
developed and glossy. In O. exaratus it is represented by a mere swelling, nearly as 
densely punctured as other parts of the thorax. In both insects there are four large 
shallowish fovez near the hinder margin of the thorax, separating the ridges; in O. 
striatus the fovez can scarcely be traced ; here the sides of the thorax at the base are 
_ parallel for a short distance, then they converge suddenly to the front. In O. sulca- 
tus they converge from the base to the apex, but present a gently convex outline, and 
the part immediately below the anterior angle is somewhat incrassated and slightly 
rounded. In O, exaratus the sides of the thorax also converge, but are straight, ex- 
cepting towards and near the anterior angles (which are depressed), where they gently 
bend inwards. The surface of the thorax is moderately densely and moderately finely 
punctured in O. sulcatus; in O. exaratus it appears under a common lens to be 
densely covered by very minute longitudinal scratches, separated by equally minute 
ridges; under a strong lens, however, punctures are visible, more especially on the 
