THE FAMILY LITUOLID^ 135. 



glazed by a thin chitinous lining. Sometimes the 

 arenaceous material composing the test is reduced to 

 a minimum quantity under certain conditions, as in 

 estuarine or brackish pools, the result being a thin 

 membranous and flexible test, as, for example, in some 

 species of the genus Tiochainniuid. 



The Endothyein,e are not so well defined a group' 

 as the two previous ; but they can be said to be 

 generally characterised by an arenaceous test com- 

 posed of calcareous particles, with a large proportion 

 of calcareous cement ; their shell- wall is often 

 distinctly perforate. There is also a tendency for 

 the internal shell structure to become cancellated, or 

 broken up into a rudely cellular structure, but not 

 to so great a degree as in the next sub-family of the 



LOFTUSIIN.^. 



The Endothykin.e is an entirely fossil group of 

 organisms, and it is well represented in the Palceozoic 

 rocks by NodosineJhi, Stacheia, EudotJi/jra, and 

 Brady ilia, whilst Inrolutina. is restricted to the 

 Jurassic series of the Mesozoic period. The genus 

 Stacheia further extends its range from the Paleozoic 

 into the Mesozoic rocks by its appearance, in some 

 abundance, in certain marls of Rhcetic and Liassic 

 ages in England and France. 



The types of subarenaceous PatellincF, as Orbito- 

 lina and Conulite,'^, are perhaps more conveniently 

 separated from the first named genus ; not on 

 zoological grounds, however, for they represent the 

 same morphological species of organism. For this 

 latter reason Carpenter and Rupert Jones treated 



