INTRODUCTION. 5g 
tata, lateralis ; disco longitudina- 
liter poris pertuso. 
GEN. 15. Patella, — Animal limax; 
testa univalvis, subconica, absque 
spira. 
GEx. 16. Dentalium.—Animal tere- 
bella; testa univalvis, tubulosa, 
recta, monothalamia, utraque ex- 
tremitate pervia. 
GEN. 17. Sabella—Animal terebella ; 
testa univalvis tubulosa , adhærens. 
(Sæpe isthmisintegris passim inter- 
cepta.) 
GEN. 18. Teredo.—Animal terebella ; 
maxillæ duæ calcareæ , hemispheri- 
cæ , antice excisæ, subtus angula- 
tæ; tes'a teres, flexuosa, lignum 
penetrans. 
GEN. 19. Serpula.— Animal nereis; 
os ringens, tentacula duo crassiora 
pone caput; testa tubulosa, contex- 
ta ex arenulis, confertim membra- 
næ vaginali impositis. 
