MAZATLAN UNIVALVES 193 



The serrations of the margin in the only perfect specimen 

 found are distinctly visible through the dried cuticle, as they 

 are also in some dead valves in other respects agreeing with 

 the shell, Below the large scales of the mantle margin appears 

 a row of gill-like flattened hairs, as in the young of L. artieu- 

 latus and albolineatus. Long. '17, lat. '12, alt. '04. 



Hob. Mazatlan ; 1 sp. off Spondylus oalcifer ; L'pool Col. 

 Tablet 897 contains the specimen. 



GENUS PTONICIA, Gray. 



Proc. Zool. Sec. 1847, p. 65. H. fy A. Ad. Gen. vol. i. p. 473. 

 Chiton, pars, auct. Plates of insertion as in Lophyrus : mantle 

 smooth. 



251. ? TONICIA FORBESII, n. s. 



? T. t. ovatd, subelevatd fad angulam 115^ brunned, olivaceo 

 varie pictd ; valvis intermediis mucronatis, sulcis injugo \l~for- 

 mibus a mucronibus projicientibus decurrentibus ; lineis diagon- 

 al ibus v aide tuber culatis ; areis later alibus sparsim punctatis, 

 ad valvarum interstitia tuber culato-corrugatis ; areis centr ali- 

 bus rugis curvatis divergentibus, in valvis terminalibus circiter 

 xiii. ; mucrone conspicuo ; limbo pallii sublcevi, lenuiori ; 

 valvarum lobis intus dcclivibus, sinu alto, lato ; jugo intus roseo ; 

 marginibus valvarum et sinus dense serratis, Jlssuris in valvix 

 intermediis und in latere utroque, in valvis terminalibus rugis 

 externis convenientibus. 



Two specimens were found of this very beautiful species, 

 which is dedicated to the memory of the learned and deeply 

 lamented. Prof. !E. Forbes, whose promised assistance, had lie 

 lived, might have prevented many errors in the present work. 

 Neither of the specimens shew any trace of imbricated scales, 

 though they may possibly exist. The structure of the marginal 

 plates closely resembles that of Lophyrus albolineatus. Loin,-. 

 '78, [lat. '45, alt. '14. 



Hab Mazatlan ; extremely rare ; L'pool Col. 



Tablet 898 contains the finest specimen; the other is in 

 Mr. Darbishire's cabinet. 

 April 1856. s 



