LAMINELLA. 325 



ally of highly " accelerated " type, neanic or adult patterns 

 appearing in the embryonic stage. In forms which have not 

 undergone degeneration of the color-pattern, the sequence in 

 ontogeny is about as follows: (1) on the second embryonic 

 whorl longitudinal streaks appear; (2) on the third whorl 

 near the end of the embryonic stage, these are replaced by a 

 few well-separated, longitudinally-protractive stripes, pi. 56, 

 figs. 6, 8, L. picta; (3) on the early neanic whorls the stripes 

 are closer, vary in direction, and often become angulated; 

 (4) on the later neanic and last whorl the stripes become zig- 

 zag, or anastomose in various patterns; (5) on the last part 

 of the last whorl, especially basally, the dark stripes be- 

 come coalescent, producing a more or less uniform blackish 

 color. 



In more accelerated species the successive patterns may 

 'appear earlier; in less accelerated forms, patterns (2), (3) 

 or (4) may persist (as in L. a. duoplicata), later patterns 

 not appearing; various stages may be left out; or degener- 

 ative change may set in at any stage, the stripes breaking into 

 dots, as in L. semivenulata, pi. 56, fig. 7, or disappearing en- 

 tirely. That such degeneration of pattern is secondary is 

 evident from the fact that the disappearance is progressive 

 from the last towards the earlier stages, as in L. helvina, L. 

 semivestita, etc. L. concinna circumcincta has a highly 

 evolved color-pattern, in which the primitive longitudinal 

 stripes have been broadly interrupted, their separated rem- 

 nants coalescing spirally to form encircling bands. Some spe- 

 cimens of L. citrina semivenulata show a tendency towards 

 a similar pattern. 



I look upon L. picta and its allies as the more primitive 

 forms of the genus, approaching nearest to the Amastrae of 

 the same islands, though it is evident that all the Laminellae 

 are rather evolved forms. Professor Hyatt held L. gravida 

 to be the most primitive Laminella, apparently on account of 

 its Amastroid shape and cuticle. This species seems to me to 

 be not primitive 'but highly evolved. The zigzag-striped stage 

 is confined to the early neanic whorls (pi. 56, fig. 1), while 

 the later neanic and last whorl have a uniform, dark cuticle 



