ACANTHOCHITES-NOTOPLAX, 33 



A. FORMOsus Reeve. PI. 1, figs. 12, 13 (enlarged.) 



Shell oblong, rather narrow ; valves very finely longitudinally 

 striated at the summit, granulated at the sides. Bright scarlet. 

 Ligament horny, thickly beset with shining white spicula at the side 

 of each valve. Length i, breadth t,t inch. (Reeve.) 



Cape Rivers, N.-W. Celebes ; one specimen. 



Chiton formosns Reeve, P. Z. S. 1847, p. 25 ; Conch. Icon., t. 26, 

 f. 173. — Adams & Reeve, Zool. ' Samarang,' t. 15, f. 8. 



Carpenter believed his MS. species Macandrellus plumeus to be the 

 same as this, although he had not, I believe, compared the types. 



His description is as follows : 



A. plumeus Carpenter. Shell subelougate, subelevated, the dorsal 

 ridge acute, mucro submedian, hardly raised, the slope behind it 

 concave. Roseate at the sides, olivaceous in the middle. Exposed 

 part of the valves small. Posterior valve subrotund ; anterior valve 

 pectinated and 5-angled around the margin; central valves strongly 

 angular, beaked ; sutures deeply encroaching on the side-areas. 

 Dorsal areas delicately and closely sublongitudinally lirulate ; lateral 

 areas distinctly defined, sunken ; central and lateral areas scaly in 

 radiating, somewhat plumose pattern. 



Interior : posterior valve hardly sinuated behind, having a slit at 

 each side, the plate between them deeply grooved outside and sub- 

 dentate, shallowly slit at the edge. Anterior valve having 5 slits, 

 the teeth angular at the slits. Girdle leathery, smooth, sometimes 

 somewhat spongy, having minute hairlets, and small tufts of hairs 

 at the sutures. Length 21, breadth 11 mill. ; divergence 120°. 



Habitat un/aiown (Mus. Cuming, no. 108.) 



Macandrellus plumeus Qp'R. MS. ; and in Dall, Proc. U.S. Nat. 

 Mus. 1881, p. 288 (no description.) 



The irregular, rugose lobes of the tail plate, behind, almost 

 amount to teeth. The head valve is hexagonal. The sculpture 

 resembles the feathers of a bird. The lateral areas are distinct, but 

 sunken instead of raised. (Cpr.) 



A. AcuTiROSTRATUS Rcevc. PI. 8, figs. 27, 28. 



Shell elongated, elevated in the middle, somewhat compressed at 



the sides ; valves obtusely keeled at the summit, smooth ; very closely 



flatly grained on each side; umbones produced, sharply beaked; 



lateral areas of the valves small, rather indistinct, concave. Whit- 



3 



