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. articu- 

 latus and albolincatus. Long. '17, lat. '12, alt. 'Odi. 



Sab. — Mazatlan ; 1 sp. off Spondylus calcifer ; L'pool Col. 



Tablet 897 contains the specimen. 



Genus PTONICIA, Gray. 



Proc. Zool. Sec. 1847, p. 65.— IT. ^ A. Ad. Gen. vol. i. p. 473.— 

 Chiton, pars, auet. Plates of insertion as in LophjTUS : mantle 

 smooth. 



251. ? TONICIA FOEBESII, n. s. 



? T. t. ovatd, suhelevata (ad angulam 115"^ brunnea, olivacen 

 varie pictd ; valvis intermediis mueronatis, sidcis injugo ^-for- 

 mihus a mucrouibiis proj icieniibus deciirrentibus ; lineis diagon- 

 alibus valde tuberculaiis ; areis lateralibus sparsim punctatis, 

 ad valvartim intersfitia tuberculato-corrugatis ; areis centrali- 

 bus rugis curvatis divergeutibus, in valvis terminalibus circiter 

 xiii. ; mucrone conspicuo ; limbo palUi mihlcBvi, iemiiori ; 

 valvarum lohis intus declivibus, sinu alto, lato ; jugo intus roseo ; 

 marginibus valvarum et sinus dense serraiis,Jlssiiris in valvis 

 intermediis una in latere uiroque, in valvis terminalibus rugis 

 externis convenientihus. 



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 albolineatiis. Long. 

 •78, [lat. -45, alt. "14. 



Hah. — Mazatlan ; extremely rare ; L'pool Col. 



Tablet 898 contains the finest specimen ; the other is in 

 Mr. Darbishire's cabinet. 



April 1856. $ 



