324 American Seashells 



areas greatly raised and with 2 convex, strong ribs of coarse beads. Anterior 

 valve with 9 convex, beaded ribs. Posterior valve very high, convex and 

 with 7 to 8 pairs of strong ribs. Interior bluish white. Girdle yellowish with 

 reddish bands; thin, narrow and with microscopic, striated scales. Uncom- 

 mon. 



Fa7nily CHITONIDAE 

 Subfamily CHITONINAE 

 Genus Chiton Linne 1758 



Outer edges of insertion plates with tiny, sharp teeth or pectinations; 

 girdle with small, hard scales that look like overlapping split peas; girdle 

 colored with alternating bars of grayish green and black; interior of valves 

 blue-green. 



Key to the American Chiton 

 Valves entirely smooth: 



Girdle scales glassy; sinus of valves narrow . laevigatus (Pacific) 



Girdle scales dull; sinus of valves wide . marmoratus (Atlantic) 



Valves with sculpturing: 



Central area with longitudinal ribs: 



Posterior valve with round pimples . . tuberculatus (Atlantic) 

 Posterior valve with radiating ribs . . virgulatus (Pacific) 



Central area smoothish and dull .... squamosus (Atlantic) 



Chiton tuberculatus Linne Common West Indian Chiton 



Plate id; figure 6-ji 



Florida to Texas and the West Indies. 



2 to 3 inches in length. Color a dull grayish green or greenish brown. 

 Some or all of the valves may have a smooth, dark-brown, arrow-shaped 

 patch on the very top. Girdle with alternating zones of whitish, green and 

 black. The scales are placed on the girdle, so that they appear slightly higher 

 than broad, while in squamosus they appear to be broader than high. Lateral 

 areas with 5 irregular, radiating cords. Central areas smooth at the top and 

 with 8 to 9 long, strong, wavy, longitudinal ribs on the sides. End valves with 

 irregular, wavy radial cords. Gills beginning at the juncture of the head and 

 foot and with 46 to 48 lamellae. A very common species on wave-dashed, 

 rocky shores. 



