CHEILOSTOMATA. 



637 



tant, caudate, and connected with one another by a slender prolonga- 

 tion of the lower extremity, so as to form a linear series " (Hincks). 

 The earliest forms of this type appear in the Cretaceous rocks, and 

 the genus still survives. The genus Eschara, as formerly under- 

 stood, has been reconstructed by modern authorities, and its most 



Fig. 483. — A, Cells of Lef>ralia pallasiana (Tertiary and Recent), enlarged. B, Cells of 

 Schizoporella unicornis (Tertiary and Recent), enlarged, c, Cells of Mucronella coccinea (Ter- 

 tiary and Recent), enlarged : a, Avicularium; o, Ovicell. (After Busk and Hincks.) 





yy > ■/' i 



characteristic forms find a place in the genus Lepralia, as at present 

 restricted. In this genus, the polyzoary may be incrusting or erect 

 (fig. 484), and the foliaceous forms may be unilaminar, or may be 

 composed of two layers of cells united back to back. The zooecia 

 are ovate, with a more or less 

 horse - shoe - shaped aperture, the 

 lower lip of which is entire (fig. 

 483, a). The species of this genus 

 range from the later Secondary 

 period to the present day. In the 

 genus Porella, the original cell- 

 mouth is semicircular, but there 

 is formed round this a secondary 

 and larger mouth which encloses 

 an avicularium. The species of 

 this genus are Tertiary and Recent. 

 451, b) resembles the preceding in 

 secondary mouth is elongated and is channelled in front, while 

 the lower lip of the primary aperture is dentate. The species 

 of Smittia are Tertiary and Recent. Mucronella is another allied 

 genus, in which the peristome (fig. 483, c) is elevated in front into a 

 more or less prominent mucro. The species of the genus are Ter- 

 tiary and Recent. 



Related to the preceding, but perhaps forming the type of a 

 separate family (Reteporida), is the genus Retepora (fig. 485), in 



Fig. 484 



-Lepralia. (Eschara) Ranvilliana. 

 Jurassic. 



The genus Smittia (fig. 

 most characters, but the 



