1873.] 



347 [Horn. 



Teuetrtosoma, n. g. 



Form subcyliiidrical, short, obtuse. 



Head deeply inserted, vertex convex, front inflexed ; no frontal stria. 



Antennte inserted on the front, antenual fossa broad and shallow, situ- 

 ated on the underside of thorax in front of the coxfe. 



Prosternum short, broad, without striaj, anteriorly subtruncate, poste- 

 riorly emarginate ; niesosternum prominent in front, received by the 

 l^rosternum, and with entire marginal line. 



Thorax nearly as long as the elytra, subquadrate, anteriorly emar- 

 ginate, at base broadly rounded. 



Elytra punctured. Scutellura minute. 



Propygidium transverse short. Pygidium double, upper portion, 

 transversely oval, feebly convex, inferior portion longitudinally concave, 

 transversely scarcely convex. 



Anterior tibiaj slender at base, dilated at apex, exteriorly finely serru- 

 late with many spinulose teeth, middle and hind tibiiB similar, the hitter 

 with the spinules less densely placed. Tarsi bi-uiiguiculate. 



This genus is closely allied to Teretrim and Xiphonotus, and apparently 

 nearly intermediate between the two. From the former it differs espec- 

 ially by the double pygidium, and from the latter by the absence of the 

 prothoracic projection in front, and the two claws to all the tarsi, 

 and the form and armature of the tibite. The vertex and front are not 

 in the same continuous curve, but the latter is flat and more strongly in- 

 flexed than the former, and longitudinally concave. 



T. chalybsBuin, n. sp. 



Form subcylindrical, short, obtuse, surface shining bluish with slight 

 tinge of green, sparsely, equally, and not coarsely punctured, antennae 

 and legs reddish-brown. Thorax subquadrate, slightly broader than 

 long, sides feebly arcuate, and slightly convergent in front. Elytra 

 slightly longer than the thorax, and scarcely longer than wide, at base 

 slightly impressed. Propygidium transverse, punctured similarly to the 

 elytra. Pygidium double, basal portion more than twice as wide as long, 

 and at distal end arcuate, surface similar in color and punctuation to 

 the propygidium ; apical portion viewed directly in front, crescentic, ver- 

 tically slightly concave, transversely scarcely convex, surface piceous, less 

 distinctly punctured and subopaque. Prosternum as broad as long, 

 moderately convex, sparsely and coarsely punctured. Meso- and meta- 

 sternvim coarsely and sparsely punctured, the suture obliterated. Length 

 .12 inch ; 3 mm. Plate 0, fig. 9. 



One specimen, Texas, received from Dr. Summers, of New Orleans. 



Plegaderus, Erichs. 



Plegaderus may be readily known from all the genera of Histeridaa 

 by the structure of the prosternum. The prosternum is broad and has 

 on each side a broad, deep channel extending from the lobe to the tip, 



