248 



MOLLTJSCA, BRYOZOA, SPONGES. 



[Ca XVII 



Fig. 279. 



Hadiolites Mortoni, Mantel!. Houghton, Sussex. 'White chalk. 

 Diameter one-seventh nat size. 

 Fig. 278. Two individuals deprived of their upper valves, adhering together. 

 279. Same seen from above. 



250. Transverse section of part of the wall of the shell, magnified to show the structure. 



251. Vertical section of the 6ame. 



On the side where the shell is thinnest, there is one external furrow and corresponding internal 

 ridge, a, b, figs. 27S, 279 ; but they are usually less prominent than in these figures. This species 

 was first referred by Mantoll to £Tippurites, afterwards to the genus Hadiolites. I have never 

 seen the upper valve. The specimen above figured was discovered by the late Mr. Dixon. 



With these mollusca are associated many Biyozoa, such as Eschara 

 and JEscharina (figs. 282, 283), which are alike marine, and, for the 



Fig. 282. 



Fig. 2S4. 



Escharina oceani. 



a. Natural size. 



b. Part of the same magnified. White 



chalk. 



Eschara disticlia. 



a. Natural size. 



b. Portion magnified. 



White chalk. 



Ventriculites radiatus. 



Man tell. 

 Svn. Ocellaria radiata, 

 D'Orb. White chalk. 



most part, indicative of a deep sea. These and other organic bodies, es- 

 pecially sponges, such as Ventriculites (fig. 284) and Siphonia (fig. 286), 



