CYCLOSTOMATOUS BRYOZOA — CANU AND BASSLEH. 



117 



This unfortunate generalization has encouraged Pergens, Stoliczka, 

 and others to give to the genus a much broader sense, and they have 

 not taken into account the nature of the pores. But one must not 

 forget that D'Orbigny made an attempt at a general classification and 

 his generic definitions alone have an exact value. 



In 1899 Gregory generalized further. He applied the term 

 Crisina to that group which the zoologists have always called 

 Idmonea, on the pretext that the pores have no morphological 

 value. It is evident that the pores have not a great value of classi- 

 fication, but they have some value, for they are never replaced one 



Fig. 34.— Genus Crisiua D'Orbigny, 1852. 



A-C. Longitudinal section, X 16, of Crisina noriuaniana D'Orbigny, 1852, (A) 

 and transverse sections, X 16 (B, C). 



Cretaceous (Coniacian) : Fecamp (Seine inferieure), France. 



D-F. Transverse section, X 16, of C. triangularis D'Orbigny, 1851 (D), and 

 longitudinal sections, X 16, one (E) in the middle of a branch, the other (F) 

 through the extremity of a branch and sho\Aing the origin of the vacuoles. 



Cretaceous (Coniacian) : Tours (Indre-et-Loire), France. 



by the other, and in a given species their form and their presence 

 are constant. 



We have discovered the ovicell of Crisina nor7naniana D'Orbigny, 

 1852, and find it is of the type of Ascosoecia. 



Summarizing the genus Crisina D'Orbigny, 1850, is perfectly 

 limited by his definition, its ovicell, and the internal structure. 

 Among the species cited by D'Orbigny, Retepora lichenoides is a 

 member of our genus Polyascosoecia, and the species of Reuss are 

 incompletely studied. Those which are described and figured in 

 Paleontologie frangaise are of the Ascosoecia type. 



