ISCHNOCHTTON. 101 



I. YERBURYI E. A. Smith. PL 20, fig. 11. 



Shell small, depressed, slightly carinated in the middle ; pale 

 gray maculated with dull green. 'Lateral and central areas and 

 anterior valve subequally reticulated all over ; apex of the poste- 

 rior valve subcentral, moderately acute ; girdle covered with very 

 minute scales, rosy-gray maculated with dull green. (Smith.) 



Length 15, breadth 8 mill. 



Aden. 



Chiton (Ischnochiton) yerburyi SMITH, P. Z. S. 1891, p. 420, pi. 

 33, f. 6. 



Only a single specimen of this species was found by Major Yer- 

 bury. The sculpture recalls that of a thimble. It is a trifle coarser 

 on the lateral, especially along their posterior margins, than on 

 the central areas. The dirty green spotting is also more noticeable 

 on the hinder edges of the valves than elsewhere. (Smith.') 



I. MACGILLIVRAYI Carpenter, n. sp. Unfigured. 



Shell elongated, small, elevated, the jugum slightly acute, valves 

 beaked ; ashen-brown or pale ashen, often elegantly painted with 

 lines or angular flames. Entire surface minutely granulose ; lateral 

 areas scarcely denned, having radiating wrinkles, not very distinct. 

 Mucro median, little elevated. Interior : posterior valve having 

 12-13, anterior valve 12-11, median valves 1 slit. Teeth subacute ; 

 eaves very conspicuous ; sinus wide, flat, smooth. Girdle closely 

 covered with delicate, subelongated, strongly lirate scales. 



Length 14, breadth 7 mill.; divergence 110. 



Tristan d'Acunha (Macgillivray, Mus. Cuming, No. 74, 92) ; St. 

 Paul's (Mus. Curning, No. 7). 



The specimens from the last locality have the teeth acute. 



This shell has the general aspect of Trachydermon albus but is 

 longer, not so sharp at the ridge, more highly sculptured, and the 

 scales strongly lirate. The pattern varies greatly in the specimens. 

 It is nearly related to I. oniscus, and a larger series of individuals 

 may prove them identical (Cpr., MS.) 



I. RETICULATUS Reeve. PI. 20, figs. 16, 17. 



Shell oblong-ovate ; terminal valves and lateral areas of the rest 

 radiately ridged ; central areas rudely and closely reticulated ; 

 dull brown ; ligament horny, rough. (Reeve.) 



West Indies (Reeve). 



