80 ISCHNOCHITON. 



I. BERGOTI Velain. Vol. XIV, PL 27, %. 51. 



Shell elongated, quite narrow, oval, convex and subangulated on 

 the median line, perceptibly narrower in front ; color a rather deep 

 brown-grayish. 



Intermediate valves unequal, rather wide, ornamented with trans- 

 verse lines impressed in the thickness of the shell, subimbricating, 

 very strong in front and on the lateral portions, where they gener- 

 ally number 3 or 4. The upper portions are smooth or marked with 

 irregular punctations only. End valves semilunar, having impressed 

 striae like the others, but more numerous, stronger and concentric ; 

 anterior valve much narrower and more angular than the posterior ; 

 intermediate valves unequal, with the lateral areas narrow, not 

 distinctly indicated ; dorsal [central] areas wide, finely punctate. 

 Border of the mantle yellowish, but little developed, without scales 

 or spines, marked by fine granulations only. ( Velain.') 



Length 15, breadth 7, alt. 4 mill. 



Island of St. Paul, on rocks in the littoral zone, rare. (French 

 Transit of Venus Expedition to St. Paul and Amsterdam, 1874). 



Chiton bergoti VELAIN, Comptes Rendus de 1'Acad. des Sci., vol. 

 83, p. 285, July 24, 1876 (name only) ; Arch. Zool. Exper. et Gen. 

 vi, p. 123, t. 4, f. 21, 22. 1877. 



The prominent features of this species seem to be the several con- 

 centric grooves along the anterior and lateral borders of each of the 

 valves, the surface elsewhere punctate. It is probably an Ischno- 

 chiton, although Velain says that the girdle is not scaly but papillose, 

 which suggests Trachydermon. It was collected only within the 

 Crater. The surface is generally corroded, and covered with cal- 

 careous incrustations and Serpulse. 



I. CONSTANTI Velain. Vol. XIV, PL 27, fig. 49. 



Shell oblong, quite thin, uncolored or yellowish-white, equally 

 obtuse at the two ends. Terminal valves unequal, semilunar, the 

 anterior more acute at the summit than the posterior ; both orna- 

 mented with concentric strise, as in the preceding species (bergoti). 

 Intermediate valves narrow and equal; lateral areas elongated, 

 moderately developed but little prominent or distinct. External 

 surface little convex, with a median angle more or less pronounced ; 

 apparently smooth, but with a strong lens seen to be ornamented 

 with fine granules in very regular series. Border of the mantle nar- 

 row, whitish or gray, and distinctly scaly. 



Length 8-9, breadth 4-5, alt. 2 mill. (Velain). 



