v< LHTBOPLB1 RA, 



(iinllr liroad, llr-hv, l>.-t with strong spike-like ipL 



L r ill- rxtrml the whole length (.ftlir f'"<>t. 



ih mo, luvadth .v> mill.: divergence 1 1.")-120 . 

 Length 68, i.n-a.lth 40 mill. 



J'.ivt.i, /V/-// , Dr. \V. B.Jones); <;<//<//"'.'/<>* (P. Ac. Coll.) : Val- 

 parai.>, Chili ( Fivmbly.) 



Chiton whiiKitu* BARNES, Amer. Journ. Science and Arts, (Silli- 

 many) vii, p. 71, t. ", f. 4, 4b. (1823). SOWERBY, Conch, rilu.-tr., 

 f. 47 (young). GMton tvberculiferui SOWKKKY, ('at. Tankerv., p. 

 29, no. 688 (1825). Chiton .</>/'// //r/-//x FREMBLY, Zool. Journ. iii, 

 p. 196, Suppl., pi. 16, f. 1 (1827). Chiton aculeatu* REEVE, Conch. 

 Icon., t. 9, f. 49. Not C. aculeatn* of DESK, et al., nor of Linn. 

 Chiton (Corephiwn) spinifents Frembl., STEARNS, Proc. U. S. Nat. 

 Mus. xiv, 1891, p. 334. 



This large, spiney species is not likely to be confused with any 

 other, being very distinct in external features as well as in the 

 peculiar insertion-plate of the tail-valve, the engraving of the inte- 

 rior (reminding one of Enoplocliiton niyer and Chiton granosus), and 

 the denticulate sinus. The girdle spines are frequently encrusted 

 with a white calcareous deposit, converting them into globular 

 pellets. The young shell also lacks slits in the posterior insertion- 

 plate (figs. 15-17, x 2) ; and the adults sometimes show an addi- 

 tional shallow notch or two near the median caudal slit. 



Subgenus ACANTHOPLEURA, 5. sir. 



Acanthopleura GUILDING, I. c. (part), and PILSBRY, The Nauti- 

 lus vi, p. 105, Jan. 2, 1893. Frantisia CARPENTER in DALL, 

 Proc. U. S. Nat. Mus. 1881, p. 284, 289, 290 (1882.) 



Acanthopleura: Tail valve having a long, many-slit insertion- 

 plate, crenulated outside ; median valves much wider across the 

 sutural-plates (or articulamentum) thau across the exposed portion 

 (tegmentum.) 



The facts which cause me to consider this the typical group of 

 Acanthopleura have been discussed above. The affinities of the sub- 

 genus are with Mnuyerin and with Mesotomnra. With the latter it 

 agrees in the coarsely spiney girdle, interior coloring, denticulate 

 sinus and long insertion-plates; but it differs from that group in 

 having a many-slit tail-plate, in the frequent (or usual) plurality of 

 side-slits, the nearly smooth exterior, etc. In the form and dentic- 



