344 CHITONID®. 
BEANELLA, Dall. (Beania, Cpr., not Johnstone.) Armor and 
girdle intermediate between Acanthopleura and Ischnochiton ; 
mucro submedian ; the lamin acute; the girdle scaly, subspinose, 
scarcely imbricated. C. Rissoi, Cuming. 
ARTHURIA, Carp. Armor thin; valves waved ; mucro posterior, 
produced; laminz acute, smooth; last valve extending forwards, 
sinus planate, laminate, smooth; girdle coriaceous, smooth or 
downy. C. filosus, Cpr. 
NUTTALLINA, Cpr. (Named in honor of Prof. Thomas Nuttall, 
a pioneer collector of Californian shells.) Shell elongated, valves 
projecting anteriorly ; mucro posterior, elevated ; lamine acute, 
smooth, elongate; central valves bifissate; sinus not laminated, 
planate; girdle spinose. Differs from Acanthopleura in the 
smoothness of the sharp teeth, in their great length and Radsioid 
slitting ; in the thrown-back mucro, which often projects beyond 
the margin; in the throwing forward of the rest of the shell, as 
in Katherina, and in the deep spongy flat sinus which interrupts 
the sutural lamine. C. scabra, Reeve (1xxxvi, 85). 
PHACELLOPLEURA, Guild. Posterior valve thrown forward, 
having six or more slits; anterior valve with five slits; middle, one 
slit; teeth very long, sharp, smooth; eaves very short; sinus 
narrow, laminz separated ; girdle thin, downy, wide, with sutural 
pores. C. porphyriticus, Reeve. 
Section I1.—Chitones irregulares. 
Tail-plate abnormal or with a sinus behind. 
E. Schizoidea. 
Tail-valve fissured. 
Ltorica, H.and A, Adams. Insertion-plates regular, posterior 
valve slit between two ridges; anterior valve with many slits, 
middle with one; teeth blunt, rugose; eaves moderate; sinus 
narrow, girdle slit behind, smooth, scaly. C.cimolius (Ixxxvi, 86). 
AULOCHITON (Shuttl.), Cpr. Mucro posterior, slightly sinuate ; 
sinus lobed; girdle covered with small scales, produced in front. 
C. Angasi, H. Ad. 
SCHIZOCHITON, Gray. Insertion-plates straight forward, deep 
slit, slits many in anterior valve, one to two in middle, few in 
posterior valve; teeth sharp, long; eaves small; sinus narrow, 
very deep; girdle slit behind, covered with minute spicule. C. 
eNCISUs. 
F. Placiphoroidea, 
Tail-valve unslit, internally ridged, mucro nearly terminal. 
ENOPLOCHITON, Gray. Insertion-plates straight forward, flat 
behind ; anterior valve with many slits, middle with one, posterior 
with none; teeth serrate; eaves moderate; sinus deep, lobed ; 
girdle large, with separate scales, and bristles between. 
Coquimbensis, Fremb. (1xxxvi, 87). 
