MICROLOPHUS PERUVIAN US. 315 



in several of its structural peculiarities, such as the cephalic plates, 

 which would be either smooth and not imbricated, or slightly carinated 

 and subiinbricated, and also the dorsal crest, which would nearly dis- 

 appear from the middle region of the body. We have examined four 

 specimens, young and adult, all agreeing in the following particulars : 



DESCR. The cephalic plates are smooth, subconvex, polygonal, un- 

 equal, and not imbricated; the largest ones (the occipital excepted), 

 may be seen upon the frontal and supraocular regions ; transversely 

 elongated upon the latter region, from four to six in number, and dis- 

 posed upon a curvilinear series ; upon the frontal region, they are 

 more or less symmetrically arranged, right and left, and irregular in 

 their outlines. The occipital plate is quite large and conspicuous. 

 A curvilinear series of moderate plates is observed on each side of the 

 occipital, extending from the posterior upper angle of the orbit to the 

 frontal region, passing between the eyes, where they meet, occupying 

 all the interocular region. The occipital, posteriorly and sideways, is 

 surrounded by small plates, constituting but one series behind, whilst 

 laterally, the same small scales extend over the temporal regions, and 

 a group of them may even be observed anteriorly, in a subtriangular 

 area, formed by the curvilinear series just alluded to. A similar cur- 

 vilinear series of small plates borders interiorly the supraocularSj 

 already mentioned, whilst the anterior and exterior areas of the supra- 

 ocular region, not occupied by the large plates, are covered with simi- 

 lar small plates. The supraciliary plates are narrow and elongated, 

 five or six in number, smallest anteriorly. The nasal plates are of 

 moderate development : those which the nostrils perforate are the 

 most conspicuous, and situated near the apex of the snout, just above 

 a line which would be the prolongation of the supraciliary ridge, and 

 separated from the rostral by a circle of minute plates. The nostrils 

 themselves are tubular, and directed outwardly backwards. As to 

 the rostral plate it is quite low, horizontally elongated, and convex or 

 subconvex above. The upper labials are narrow and elongated, ten 

 in number : the seven anterior increasing in size backwards, and fol- 

 lowed by three quite small and irregular ones, beneath which a series 

 of minute plates is observed. One series of supralabials is likewise to 

 be seen, resembling the labials, diminishing backwards, though not 

 extending beyond the anterior third of the orbit. The phrenic region 

 is protected by a few plates of moderate development. The sub- 



