CONCHOLOGY. 
56. Patella, Shell thick ; the crown imperforate 
and inclining anteriorly ; spire none ; the margin 
entire: muscular impression elliptic, somewhat 
truncate before and constricted at the sides. 
Includes Patella vulgata, pellucida, and parva. 
57. Emarginula, The crown imperforate ; spire 
none ; the margin cloven or notched anteriorly, 
Includes Patella Fissura. 
58. Pileopsis. Crown imperforate, hooked at the 
tip ; the margin very entire. 
Includes Patella ungarica, antiquata. 
59. Calyptrea, Crown imperforate, central, erect ; 
the internal cavity furnished with an involuted 
lip. 
Includes Patella Chinenis. 
60. Fissurella, Crown perforated ; the margin 
very entire, 
Includes Patella Apertura, Greeca, 
2. BULLADZ, 
Shell open, involute; the spire mostly concealed 
or none. 
61. Bull@a, Shell very thin, partly and spirally 
involute at the upper part, without produced 
spire or pillar. 
Includes Bulla aperta, B. plumula, and others. 
62. Bulla, Shell hard, somewhat cylindrical, 
without spire none; truncate at top: aperture 
as long as the shell. 
Includes Bulla cylindrica, ampulla, &c, 
