522 MR F. R. COWPER REED ON 



specimen is imperfect, but the general outline of the body is an elongated oval, with a 

 very weakly convex surface, slightly carinated longitudinally down the middle. It is 

 composed of a double series of overlapping plates, like the scales of a fir-cone, with their 

 surface replaced by a film of yellow oxide of iron, just as Barrande described in his 

 specimens, but where this has broken away we can see the transverse lamellae of the 

 plates, as in the typical examples of Tuvrilepas. The lateral plates composing the body 

 are arranged in pairs in two longitudinal series on opposite sides of the median line, 

 and their longer axes are inclined obliquely to this line, pointing forwards and making 

 an angle of about 60° in the posterior part of the body, but the angle becomes increas- 

 ingly more acute towards the anterior end till the last pair forming the apex make an 

 angle of only 10°-15° and have their axes slightly curved inwards. The arrange- 

 ment of the plates in pairs is rather obscured, owing to the poor preservation of the 

 fossil, and it is impossible to determine the precise number, but there seem to be ten or 

 eleven. Towards the anterior end they are more closely placed together, and overlap 

 to a greater extent. The plates have the usual kite-shaped outline, but their margins 

 are more or less broken, and they overlap in the usual way from behind forwards. They 

 become rather narrower and more elongated in shape towards the anterior end of the 

 body, and their apices are freer for a greater part of their length, while the more slender 

 tapering shape of the last two or three pairs gives to them the appearance of spines. In 

 all the posterior plates which are sufficiently preserved the usual submedian sharp fold is 

 seen, but in the foremost two or three elongated plates there are in addition two very 

 narrow submarginal folds, one on each side of the median line. The same feature is 

 noticeable in some isolated plates from the same horizon and locality, and seems to char- 

 acterise the terminal plates. The two rows of median plates can be traced only in places 

 in this specimen and for the most part are obscure, but the general shape of the plates 

 and their arrangement agree with what is seen in the Whitehouse Bay type-specimen. 



The variation in the shape of the lateral plates is seen to be due to their different 

 positions in the series composing the body ; and probably some corresponding change 

 occurs in the median series, as is suggested by isolated plates. The anterior lateral 

 plates in the specimens of T. Peachi figured by Etheridge and Nicholson (op. cif.., figs. 

 9, 10) are much less well preserved than the figures would lead us to infer, and no 

 definite conclusions can be drawn from them, but they do not seem to be so attenuated 

 as in the example from the Starfish bed (Plate, fig. 1). There is no evidence of the 

 body being completely surrounded by plates, and the nature of the ventral side of the 

 organism is unknown, but it may have been only membranous. 



In consequence of the re-examination of the type-specimens of T. Peachi and the 

 evidence afforded by the specimen from the Starfish bed, it appears that a certain 

 amount of revision of Etheridge and Nicholson's definition of the species is necessary ; 

 and in place of their summary of the specific characters the following may be substituted. 

 It must still be somewhat incomplete, owing to the nature of the material available, but 

 it marks a step forward in the comprehension of this peculiar organism. 



