94 PATELLA-SCUTELLASTRA. 



infrequent. Parallel mutations occur in Acmcea pelta, Patella gran- 

 iilaris, Patina pellucida, etc., etc. 



Var. MINIATA Born. PI. 26, figs. 22-27. 



Shell thin, varying from depressed and broadly ovate to conical 

 and narrowly ovate ; sculptured with numerous acute unequal radi- 

 ating riblets, more or less destinctly decussated by growth-striae. 

 Riblets white or yellowish, interstices occupied by red rays ; the 

 young speckled and blotched with red (rarely brown or purple- 

 black). 



Interior having an opaque-white central area, the outer portion 

 transparent and showing the color-rays. 



Length 70, breadth 58, alt. 13 mill, (normal.) 



Length 58, breadth 42, alt. 18 mill, (more elevated specimen; figs. 

 23, 24.) 



There is great variation in the form, still greater in the sculpture 

 of this shell. Some young specimens are nearly smooth, having fine, 

 subequal radiating riblets, scarcely decussated, whilst others have 

 the riblets distinctly cut into close, compressed beads by the con- 

 centric sculpture. 



In young shells the apex is much nearer the anterior end than in 

 adults. 



P. ELECTRINA Reeve. PI. 18, figs. 33, 34. 



Shell orbicular, attenuated in front, rather depressed ; sharp at 

 the apex ; radiately densely ridged, ridges rough, irregular, bluntly 

 squamate. Light fulvous, rusty about the apex and between the 

 ridges. Interior transparent white. (Rve.*) 



Australia. 



P. eleetrina RVE., Conch. Icon., f. 55. Dec., 1854. 



Of a transparent texture, stained with amber rust about the apex 

 and between the ridges, the color showing conspicuously through in 

 the interior, (five.) 



Compare P. miniata and P. lowei. 



Section SCUTELLASTRA H. & A. Adams, 1858. 



Scutellastra ADS., Genera Rec. Moll, i, p. 466, types P. gorgonica 

 Humph., pentagona Born, plicata Born. Olana ADS. /. c., type P. 

 cochlear Gmel. 



Inner layer of the shell opaque, porcellanous, not iridescent nor 

 fibrous in texture. 



