ON THE PERMIAN CHITONlDiE. 245 



bat faintly indicated. In old plates the later lines of growth 

 are occasionally deeply marked, and might almost be termed 

 sulcations. The same plates are also very thick, especially 

 about the median region and posterior margin. In many plates 

 the rounded longitudinal ridge, and lateral sulcations which 

 emanate from the apex and ornament the dorsal area, can scarcely 

 be detected ; and the oblique angulations of the same area are some- 

 times wanting. The absence of these characters is chiefly con- 

 fined to young examples. The second and the seventh plates 

 are more acutely angulate medianly than those placed between 

 them ; the central ones are the most obtuse, their height being 

 retained by a slight increase of width. In full-grown interme- 

 diate plates the internal surface is deeply excavated parallel with 

 the posterior margin ; the extreme posterior, lateral, and lower 

 part of the anterior margins of the same surface is raised into a 

 flattish rim-like projection; the central portion of this surface is 

 prominent. 



The external surface of the plates is finely granulated, the 

 granulations appearing to be somewhat regularly arranged in 

 well-preserved specimens. In one or two instances I have met 

 with plates, apparently belonging to this species, which have a 

 coarsely granulated surface, very different from that of the gene- 

 rality of specimens. In such cases the granulations have an 

 irregular, though a somewhat linear, arrangement. One of my 

 intermediate plates is ornamented with obliquely transverse nar- 

 row bands of a darkish brown hue, which I imagine may be 

 traces of colour-ornamentation. They may certainly be but acci- 

 dental markings, resulting from fossilization; but their regula- 

 rity, and the occurrence of colour-markings on other Permian 

 species, seem to indicate an organic origin. 



C. Lqftusianus appears to have been about an inch-and-half or 

 more in length. The longest intermediate plate (which is not 

 the second) in my collection is one-fifth of an inch in length ; a 

 posterior plate is exactly the same. I have not the anterior plate 

 equally full-grown to measure; but, from the length of those 

 measured, it may be inferred that they belonged to an individual, 

 or individuals, somewhat more than an inch-and-half long. The 



VOL. IV. PT. IV. 2 G 



