Table 2.

Proportions of transition per lineage (T) necessary to account for the greater increases in number of nonplanktonic species relative to species with planktonic larvae as estimated from Hansen’s (6) data

Gastropod group	T	CT, %
Buccinidae	0.10	68.0
Fasciolariidae	0.23	29.6
Mitridae	0.50	13.6
Nassariidae	0.30	22.7
Olividae	0.40	17.0
Volutidae	0.18	37.8

Contribution of developmental transitions (C_T) to increase in numbers of nonplanktotrophs if T = 0.068 (see Discussion).