198 MAZATLAN UNIVALVES 



GENUS CHITON, Linn. 



Chiton, pars, auct. H. fy'A. Ad. Gen. vol. i. p. 474. Acan- 

 thopleura, G-uild. ; Gray in Proc. Zool. Soc. 1847, r p. 67. 

 Margin spinose : insertion-plates in terminal valve rnany- 

 lobed, in middle valves bi-lobed. 



257. CHITON FLAVESCENS, n. s. 



Cli. t. ovatd, valde depressd (ad angulam 150j flavidd, 

 aurantio maculatd ; valvis latis, marginibus subrotundatis, 

 interstitiis curvatis, valde mucronatis ; areis lateralibus et jugo 

 indistinctioribus ; mucrone parvo, superiore ; totd superficie 

 granulis rugulosis confertim instructd, hand punctulatd ; limbo 

 pallii crasso, sublcevi, ad marginem spinulis tenuibus, erectis, 

 planatis instructd ; valvarum lobis, magnis, arcuatis, simi 

 maxima ; marginibus valvarum intermediaruin fissurd duos in 

 lobas divisis, quarum unaparva, lineis punctorum utrdgue in 

 parte adjugum decurrentibus ; valvarum ultimarum marginibus 

 subacutis,jissuris circiter x. 



This is the least uncommon of the small Chitons, six speci- 

 mens having been found of it. It is distinguished by its yellow 

 colour, great depression, and small strong mantle margin, 

 without covering, except at the margin where a fine row of 

 transparent flattened hairs may be seen. The smaller lobe on 

 the margins of the inner valves is- bounded by two rows of 

 holes which proceed to the jugum. Long. '16, lot. '11, alt. '3. 

 Another specimen, rolled into a ball, is larger. 

 Hob. Mazatlan ; on shells, very rare ; If pool Col. 



Tablet 906 contains the largest specimen ; another in situ 

 on a broken crevice of Crepidula ; and 2 separate valves. 



GENUS ACANTHOCHITES, Eissg. 



G-ray, Proc. Zool. Soc. 1847, p. 66 : H. $ A. Ad. Gen. vol. i. 

 p. 482. Chiton, pars, auct. Mantle with tufts of bristles. 



258. ACANTHOCHITES AEKAGONITES, n. S. 



A. t. elongatd, elevatd (ad angulam 110% pallido-fusca, 

 olivaceo et roseo variepictd : valvis intermediis valde mucronatis, 

 interstitiis a mucronibus valde divergentibus ; jugo lato, pallido, 



