138 Zoological Society. 



tured, excepting on the disc, which is almost impunctate ; emargi- 

 nated in front, the emarginated portion in the form of a segment of 

 a circle ; the lateral margin slightly rounded. The hinder part of 

 the thorax and the middle are equal in width ; the fore-part is slightly- 

 contracted. The elytra are ovate, and but little convex ; they are 

 depressed at the suture, most distinctly so near the scutellum. The 

 lateral keel is very prominent, and extending from this keel to the 

 middle of the elytron are distinct transverse furrows, the interspaces 

 of which are convex, and about equal in width to the grooves. The 

 apical portion of the elytra is moderately produced. The three basal 

 segments of the abdomen, as well as the metasternum, are covered 

 with slightly irregular longitudinal rugae : the terminal segment is 

 punctured. The prosternum and mesosternum are coarsely punc- 

 tured, and the punctures are confluent. 



This is a small species compared with N. lavis (being about the 

 size of N. nodosa) ; its form is more elongated and much less convex. 

 The lateral margins of the thorax form an even curve from the front 

 to the back. 



The specimens from which the above description is drawn up were 

 found by Mr. Darwin in the month of September, on the sandy 

 plains of Bahia Blanca. 



Nyctelia rugosa. Nyct. nigra, opaca, ovata; thorace distincte 

 punctato ; elytris valde rugosis, sulcis duobus, suturam prope, Ion- 

 gitudinalibus et interruptis, impressis. 



Long. corp. 7| ; lat. 4f . 



Hab. San Bias (near Rio Negro) and Bahia Blanca. 



This, which is a small species compared with N. Icevis, approaches 

 that species in general form, but the thorax and elytra are less con- 

 vex. The head is coarsely punctured in front. The thorax is coarsely 

 punctured, and the punctures are numerous, excepting on the disc : 

 a groove runs parallel with and close to the margins, but at the 

 posterior margin it is interrupted in the middle. The elytra are 

 convex, and of a short ovate form, and the apical portion is but little 

 produced ; their width is about one-fifth less than the length : the 

 whole upper surface is covered with coarse and very irregular ruga?. 

 Four somewhat interrupted and irregular striae run parallel with and 

 near the suture, and there are two abbreviated oblique striae near the 

 scutellum. Besides the ordinary rugae of the elytra, there are more 

 marked rugae, which, though very irregular, have a tendency to a 

 transverse disposition, and these cover the outer half of each elytron. 

 The prothorax is punctured beneath and rugose between the legs, as 

 well as the mesosternum and metasternum. The three basal seg- 

 ments of the abdomen are covered with fine but distinct rugae, and 

 though these rugae, for the most part, have a longitudinal direction, 

 they are much more irregular than in most species of the genus. 

 The two terminal segments are punctured, but in the penultimate 

 segment the punctures are very few in number, and confined to the 

 sides. The spines at the apex of the anterior tibiae are more slender 

 and proportionately longer than in N. Icevis, 



