428 



MOLLUSCA. 



comprehensive genus of this family is Lepralia (fig. 269, A), 

 in which the coencecium usually forms circumscribed crusts 



Fig. 269. A, A few cells of Lepralia violacea (Pliocene and Recent), magnified ; B, Cellcporn 

 coronopus, of the natural size, and a portion of the surface enlarged (Pliocene) ; c, A small 

 piece of Salicornaria crassa, of the natural size and enlarged (Pliocene) ; D, Lunulites qiwtdrata, 

 of the natural size, and a small portion of the upper surface enlarged (Tertiary) ; E, A frag- 

 ment of Scrupocellaria elliptica, viewed from behind, enlarged (Tertiary) ; F, A small piece of 

 Crisia denticulata (Tertiary), enlarged ; G, A fragment of Tubulipora flabellaris (Tertiary), 

 enlarged ; H, A fragment of Diastopora simplex, enlarged (Tertiary) ; i, A piece of Vincvlana 

 Haidingeri, natural size and enlarged (Tertiary) : j, Idmonea fenestrata, natural size and en- 

 larged (Tertiary) ; K, Hornera reteporacea, natural size and enlarged (Tertiary). (After Busk 

 and Reuss.) 



growing upon foreign bodies, and the front wall of the cells 

 (though sometimes more or less minutely perforated) is com- 



