86 PROCEEDINGS OF THE 



2. Sulcochiton, De Ryckholt, 1862. (Jour, de ConcJujl., x., p. 

 259.) This name was proposed by Baron de Ryckholt for a small 

 buccal plate, supposed to be that of a Chiton, from the Carboni- 

 ferous limestone of Vise. The plate is described as divided into 

 two equal halves by a half obliterated groove, passing from the 

 summit to the margin. Too little is known about this fossil to 

 readily accept it as the basis of a generic division. Our species, 

 Chittmellus Bennieanus, has the plate similarly grooved, but other- 

 wise differs from de Ryckholt's type. 



Two recent genera may perhaps be found to comprise some of 

 the old species, viz., Schizochiton, Gray, and Enoplochiton, Gray. 

 In the former the plates are as long, or longer than they are wide, 

 with the apex of each plate situated posteriorly, and directed back- 

 wards ; this will, perhaps, include Chiton priscus, Minister, and 

 the like. 



In Enoplochiton, the valves are subcordiform, and the characters 

 are very much those of the fossil Chiton Loftiisiamis, Kirkby. 



Chiton Dalriensis, sp. nov. — (PL L, figs. 1-12, 13 and 14.) 



Sp. Char. — Anterior plate nearly semicircular, very convex and 

 somewhat high. Front margin rounded, posterior margin rather 

 concave, forming a shallow re-entering angle. Apex minute, most 

 elevated point of the plate, quite blunt in fact, rather depressed 

 than otherwise ; two indistinct radii pass towards the front, and 

 faintly subdivide the plate into three areas, of which the lateral 

 are by far the larger. 



Intermediate plates — (one of the) twice, or a little more, as broad 

 as long, transversely elongated, varying a little in length according 

 to the position of the plate in the mollusc ; much arched longitu- 

 dinally, with a bluntly carinated median line ; the plates do not 

 taper near the lateral extremities, but retain the same size at the 

 latter as in the central line. The front margin is medianally 

 slightly concave, and, at the side rounded ; posterior margin 

 convex laterally, curving slightly inwards, and outwards to the 

 apex ; extremities broadly rounded. Apex acute, and more or less 

 produced, placed posteriorly, and remote from the front margin. 

 A division into lateral and dorsal areas is hardly perceptible, but 

 when so the lateral are small, curved, and narrow ; the dorsal bears 

 the carinated ridge, becoming blunter towards the front of the 

 plate, and it does not appear to be sub-divided by any sulcations. 





