CHITON. 157 



Lateral areas strongly raised, and sculptured with three or four 

 low radiating ribs bearing at irregular or regular intervals low 

 rounded pustules ; or having no radiating ribs, the pustules few and 

 irregularly scattered; posterior border of each valve generally den- 

 ticulated. Central areas smooth in the middle, but sculptured along 

 the diagonal lines with a series of short ribs bent in the shape of a 

 reversed $ (figs. 66, 67). End valves bearing radiating series of tuber- 

 cles, or with only a few scattered tubercles. Mucro near the front 

 margin. 



Interior light blue or light green. Sutural plates lighter, highly 

 arched, the sinus deep, narrow, angular, the straight dentic- 

 ulate portion from i to i the length of a sutural-plate. Anterior 

 valve having 13, central valves 1, posterior valve 12 slits. 



Girdle alternately whitish and brown or green, finely scaly. 



Length 36, breadth 22 mill. 



St. Thomas and St. Croix (Swift) ; Jamaica. 



Chiton squamosus denticularis, etc., CHEMNITZ, Conchy]. Cab. x, 

 p. 372, t. 173, f. 1689. Chiton viridis SPENGLER, Skrivter af 

 Naturhistorie-Selskabet. iv, p. 70, t. 6, f. 5 (1797). WOOD, 

 General Conch., p. 15 (1815). Chiton foveolatus SOWERBY, Charles- 

 worth's Mag. of Nat. Hist. 1840, p. 290; Conch. Illustr., f. 60. 

 REEVE, Conch. Icon. t. 6, f. 28. Chiton costatus C. B. AD., Proc. 

 Bost. Soc. Nat. Hist. 1845, p. 8. Chiton (Lophyrus) gemmulatus 

 SHUTTLEWORTH, Bern. Mittheil. 1853, p. 75. 



Doubtful references: Chiton squamosus, testa septen-valvi-striata, 

 etc., CHEMNITZ, /. c. x, p. 374, t. 173, f. 169Q,= Varietet af Chiton 

 undatus, SPENGLER, Skrivter af Naturhistorie-Selskabet, iv, p. 69 

 (1797). Cftifcw tessellatus WOOD, Gen. Conch., p. 23 (1815). 

 Chiton excavatus (Gray) SOWB., Conch. 111., f. 131 (never de- 

 scribed.) 



This species is well distinguished by the series of short curved 

 wrinkles along the diagonal latero-posterior edges of the otherwise 

 smooth central areas, and by the sutural denticulation, when this is 

 developed, which is by no means always the case. The diagnostic 

 features of the species are stated with great clearness by the Danish 

 naturalist Spengler, and also by Chemnitz, but the figures given by 

 them are poor. There is great variation in the development of the 

 pustules upon the lateral areas and end valves. 



