272 CALLISTOCHITON. 



? Chiton pulchellus C. B. AD., Cat. Panama Sh., p. 243 (in part). 

 " Chiton pulchellus" CPU., P. Z. S. 1865, p. 27Q. Callistochiton 

 pulchrior CPR., MSS. 



Not Callistochiton pulchellus of Carpenter's M8S. Not Chiton 

 pulchellus of d'Orbigny, Voy. dans I'Ame'r. Merid., p. 489. 



The netted sculpture of the dorsal areas is unlike other species 

 from the western coasts of the Americas. Figures 3-6, drawn by 

 the author, should enable any one to identify the species readily. 

 The small size is also rather characteristic, as well as the profile of 

 the posterior valve (fig. 5.) 



I have but little doubt of the identity of Carpenter's C. pulchrior 

 (=0. pulchellus Cpr., P. Z. S. 1865, p. 276) with the true C. pul- 

 chellus of Gray. Carpenter separated pulchrior from pulchellus 

 after studying specimens supposed to be of the latter species sent 

 him by Cuming ; but it is clear to me that Cuming's identification 

 was erroneous, and therefore the position taken by Carpenter 

 becomes untenable. 



Drawings of the form called pulchrior, prepared for Carpenter, 

 are reproduced on my plate 59, figs. 21-26. The sculpture is not 

 well rendered, and if the drawing is accurate, the tail-plate differs 

 somewhat in profile. 



Gray's description of pulchellus is not as good as Reeve's and his 

 figure (pi. 60, fig. 1) is poor. The detail figure given by Reeve is 

 copied on pi. 60, fig. 2. Gray's description is as follows : 



Shell oblong, elongate, slightly keeled, yellowish-white. End 

 valves distantly, unequally, radiately ribbed; lateral areas of 

 the middle valves with two broad, regular ribs ; central area closely 

 and deeply punctured. Margin yellowish-white, with very minute 

 bran-like scales. The ribs of the lateral areas are rarely bifid. 



Length f, breadth -J of an inch. [=about 9x4 mill.] 



Inhab. Arica, Peru, Rev. W. JELennah, Brit. Mus. (Gray.) 



The species described from Arica by d'Orbigny is in all prob- 

 ability the same as Gray's form, but the figures are very poor. The 

 original description is here translated : 



C. bicostatus d'Orbigny. (PI. 59, figs. 43, 44). Shell oblong, 

 swollen and obtuse, entirely whitish. Anterior and posterior valves 

 sculptured with broad, radiating ribs and some concentric lines of 

 growth. Lateral areas of the intermediate valves each ornamented 



