LeConte.] 



TOMICINI. 345 



tra deeply striatopunctate, interspaces more convex behind: second elevated, 

 forming a small cusp at the posterior declivity; posterior process as in the 

 preceding, but shorter and stouter, with the three teeth of nearly equal 

 length, the outer one broad, and not very clislinctly separated from the 

 upper one; the inferior ona a little shorter and acute. Ventral segments 

 opaque, densely punctured; fifth sometimes finely earinate, sometimes feebly 

 tuberculate. 



Cape San Lucas, Lower California; Mr. Xantus; also found in Mexico. 

 This species is allied to the preceding, but is less elongate, the pro thorax 

 being but little longer than wide, and the deep impressed dorsal line is 

 longer, and not terminated in front by a short, transverse impression. The 

 sexual characters, as will be seen, are quite different. 



5. P. punctulatus Chap., Mou. Plat. 199, f. 110, 9. 

 Texas, allied to the preceding, and apparently differs only by the last 

 ventral segment having a strongly marked tubercle. Unknown to me. 



Sub-family II. SCOLYTID^E (genuinf). 



The characters by which this sub-family differs from the Platypodida have 

 been already sufficiently pointed out; in other respects the species differ 

 greatly according to genus and tribe, and the chief peculiarities will be 

 pointed out under the appropriate heads. 



The genera which occurs in our fauna indicate the following tribes: 



1. Prothorax not prolonged over the head, which is oblong 



and prominent; tarsi with fourth joint smaller or in- 



distinct; third joint usually bilobed ............... i>. 



Prothorax prolonged over the head, which is deeply im- 



mersed and globose; tarsi filiform, 5 jointed ........ TOM HI M. 



2. Ventral surface ascending obliquely, .................. s< o i. v n M . 



" " regularly cylindrical .................. IIYMSIM. 



Tribe I. 



Although the genera of this tribe are the farthest removed from (70*- 

 sonida by their characters; they are in some respects the most nearly allied 

 to Platifpu*, with which the family must naturally commence, on account 

 of the relations between the latter and Brenthidm. 



The head is globose, or nearly so, and deeply immersed in the prothorax : 

 the eyes are transverse, sometimes divided, (Xyloterus); the front is not 

 prolonged into a beak; the antenna} are inserted near the base of the man 

 dibles; the scape is long and stout, the funicle short, composed of from or.e 

 to five joints, the mass large, compressed, varying in form and structure ac 

 cording to genus. Prothorax more or less cylindrical behind, prolonged in 

 front over the head aid much rounded, so that the anterior opeii;iu r I'.- 

 cv.nes very oblique, or even smietimss, almost horizontal; fie sculpture i-. 

 peculiar, and consists for a greater or less distance from the apex of sharp 

 Granules, or little spines: behind, the surface is smooth or \ ur.ct 



TROC. AMEll. PHI LOS. SOC. XV. 90. 2ll 



