1873.] 3"±T [Horn. 



Teretrtosoma, n. g. 



Form subcylindrical, short, obtuse. 



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



Antennae inserted on the front, antennal fossa broad and shallow, situ- 

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



Presternum short, broad, without striae, anteriorly subtruncate, poste- 

 riorly emarginate ; mesosternum prominent in front, received by tiie 

 prosternum, and with entire marginal line. 



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

 ginate, at base broadly rounded. 



Elytra punctured. Scutellum minute. 



Propygidium transverse short. Pygidium double, upper portion, 

 transversely oval, feebly convex, inferior portion longitudinally concave, 

 transversely scarcely convex. 



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

 late with many spinulose teeth, middle and hind tibiae similar, the latter 

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



This genus is closely allied to Teretrius and Xipltonotus, 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 tibiae. The vertex and front are not 

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

 dexed than the former, and longitudinally concave. 



T. chalybaeum, n. sp. 



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

 tinge of green, sparsely, equally, and not coarsely punctured, antenna} 

 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- 

 sternum coarsely and sparsely punctured, the suture obliterated. Length 

 .12 inch ; 3 mm. Plate 5, fig. 9. 



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



Plegaderus, Erichs. 



Plegaderus may be readily known from all the genera of Histeridaj 

 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, 



