350 



possibly be regarded as the result of the superficial budding and be intended to 

 protect the numerous new zocecial rudiments, which arise everywhere on the 

 surface of the colony between and outside of the older zooecia. This form of 

 budding may also be rendered easier by the more or less erect position of the 

 zooecia, as the new zooecia are in fact laid down in the hollows between the 

 older, so that a larger or smaller part of the walls of the latter come to take 

 part in the boundaries of the new zooecia. 



Family Petraliidae n. f. 



The zocecia which are only rarely provided with spines have scattered pores 

 and an aperture somewhat variable in form, the proximal margin of which is 

 in most cases provided with 1 — 3 extraopercular teeth. Hinge- teeth may be want- 

 ing or present. The operculum, which may be more or less chitinized, is often 

 almost membranous and not distinctly separated from the compensation-sac. A 

 peristome is wanting or only weakly developed. Aviciilaria occur in all the spe- 

 cies in varying positions, but one or several, obliquely placed avicularia usually 

 occur just proximally to the aperture, and these may be situated on a rostrum- 

 like projection of varying form, which in rare cases may appear without being 

 accompanied by avicularia. The ocecia, which are first laid down after the cryp- 

 tocyst of the distal zooecium is completed, consist of a membranous ectoooecium 

 and a calcified endoooecium provided with verj^ small, closely placed pores. An 

 ooecial cover seems to be wanting. The distal half of each lateral wall is pro- 

 vided with 3 — 8, as a rule few-pored, very rarely uniporous rosette-plates. With 

 few exceptions the colonies are free, one-layered, laminate, and in such cases the 

 basal wall of the colony is provided either with numerous pores or more fre- 

 quently with one or a few pore-chambers placed at the distal end, from which 

 radical fibres sometimes issue. 



To this family I must refer the following species, of which I only know the 

 first 6 from personal observation: Petralia undata Mac Gillivr. \ ^Lepralia<^ japonica 

 Busk, L. rectilineata Hincks, y Mucronella^ castanea Busk, M. bicuspis Hincks, M. 

 porosa Hincks, M. vultur Hincks, M. Elleri Mac Gillivr.^ M. aviculifera Hincks, 

 M. magnifica Busk, M. bisiimata Smitt, M. Thenardi Kirkp., ^Lepralia<^ dorsiporosa 

 Busk and L. taberosa Busk. To these must be added two undescribed species from 

 Singapore, of which the one, belonging to the same group of species as M. porosa, 

 is remarkable for possessing two lateral plates for the attachment of the occlusor 

 muscles of the operculum, similar to those known from the genus Chaperia. As 



61, p. 141. ' 61, p. 135. 



