318 
✓ 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Acanthochitona diegoensis Pilsbry, 1893 
Tryon and Pilsbry, Manual of Conchology, 15:25; PI. 12, figs. 52-54. 
Shell oblong, rather elevated, carinated, the side-slopes straight. Color 
buff or light gray, mottled oil the sides with olive or olivaceous black; 
girdle light green with whiter sutural tufts. The intermediate valves are 
rather minutely and acutely beaked when not eroded; are wide posteriorly, 
tapering anteriorly, but the girdle does not encroach much at the sutures. 
Dorsal areas narrowly triangular, having about a dozen, flattened, longi¬ 
tudinal striae separated by narrower grooves. Latero-pleural areas covered 
with a rather coarse but regular scale-like granulation, the granules flat, 
oblong. Posterior valve having the tegmentum covering the greater part 
of the articulamentum, somewhat diamond shaped, wider than long, with 
the prominent mucro at the posterior third. Interior blue-green; sinus 
rather wide, angular; sutural laminae moderate sized, rounded. Posterior 
valve obscurely bilobed behind, gently curved upward in the middle of the 
posterior insertion plate. Girdle densely clothed with rather long, light 
green spicules, and having 18 or 20 tufts of longer whiter spicules, the 
tufts usually not very conspicuous, and sometimes a few of them are lack¬ 
ing. Length, 19, breadth, 9 mm.; divergence, 110°. Length, 18^4, breadth, 
8 mm.; divergence, 110°. Length, 11, breadth, 6 mm.; divergence, 110°. 
(Tryon and Pilsbry, Manual of Conchology.) 
Type in Philadelphia Academy of Sciences. Type locality, San Diego, 
California. 
Range. Catalina Island and Newport to San Diego, California. 
Described as A . arragonites var. diegoensis Pilsbry. 
Acanthochitona avicula Carpenter, 1866 
Proceedings of the California Academy of Sciences, 3:211. Tryon and Pilsbry, 
Manual of Conchology, 15:24. 
A. t. A. arragonitei forma magnitudine, pallio, et indole simillima; 
sed sculptura et laminis terminalibus diversa; jugo longitudinaliter sulculis 
circ. vi. instructs, interstitiis quasi planato-squamosis; umbonibus latis; 
areis diaganalibus haud definitis; lateribus, squamis (quoad magnitudinem) 
maximis, planatis, ovalibus ornatis, seriebus indistinctis divergentibus in¬ 
structs; mucrone parvo, antice sito; colore livido et olivaceo-fusco varie 
tincto; laminis insertions valv. lat. ut in A. arragonite; antica, fissuris v. 
Long., 0.16; lat. 0.10. (Carpenter.) 
Shell very similar to A. arragonites in form, size, girdle, and general 
habit; but the sculpture and terminal laminae are different. Dorsal ridge 
having about 6 longitudinal grooves, the intervals appearing flatly scaled; 
[920] 
