ANIMALS. 203 



convex margin ; occupying the lower half of the margin of each lateral division of 

 the dorsal areas. Line of demarcation between the dorsal and the lateral area rather 

 slightly defined. Dorsal area bisulcated medio-longitudinally ; the sulcations shghtly 

 divaricating. Lateral areas narrow. 



Chiton Loftiisianus (my discovery of which has elsewhere been noticed^) is a pretty 

 species, and appears to have been about two inches in length. The above description 

 will probably enable those conversant with the family to decide as to which genus it 

 strictly belongs ;^ and for this purpose I have taken some pains in endeavouring to 

 ascertain the character of the apophyses or processes of insertion of the plates, one of 

 which, belonging to an intermediate plate, I have fortunately been able to free from its 

 investing matrix. The representations of the intermediate plates in PI. XVI will afford 

 an idea as to their varying form : fig. 11 is suspected to be the second, considering the 

 cephalic plate as the first one: fig. 13 may be the third, or one of those behind it: 

 fig. 12 is perhaps the seventh or penultimate plate. Fig. 9 represents the cephalic 

 plate, which has the apex broken off. Fig. 10 is a representation of the caudal plate, 

 which, however, does not give so clear an idea of its form as could be desired ; 

 owing to the margin of the anterior side {left in the plate) being too much elevated : 

 the consequence is, that this margin appears to be more deeply smuated than it really 

 is, and the anterior side is apparently larger than the posterior, which is quite the 

 reverse'; and, on the other hand, the sinuated character of the opposite or posterior 

 margin is not represented. The posterior portion of the caudal plate is slightly 

 concave medio-longitudinally. 



This is an extremely rare species, having only occurred to me in the Shell-limestone 

 of Humbleton Hill. I found two plates of what appear to belong to a Chiton, in 

 a fragment of Permian Limestone from Kirkby Woodhouse, Notts, sent to me by 

 Mr. E. W. Binney of Manchester. 



Order Ctenobranchiata, Schweigger. 



Pectinibkanchiata, Cuvier. 



Diagnosis. — "Branchise in the form of sessile, pectinated ridges, contained in a 

 cavity." (Fleming.^) 



Dr. Fleming has divided this group into two sub-orders, namely, Holostomata and 

 Solenostomata, respectively depending on their shell having the lip of the aperture 



1 Vide Annals and Magazine of Natural History for November, 1844. 



2 Mr. J. W. Salter seems to think, that it is a species oi Helminthochiton (vide Quarterly Journal of 

 the Geological Society, vol. iii, part i, p. 51) ; but I cannot agree to this if Helminthochiton Griffithi is to 

 be considered as the type of this genus. 



3 Britiih Animals, p. 225. 



