SIPHONIDA. 511 



Xylophaga is represented by the closely allied Xylophagella 

 of the Cretaceous. 



In the genus Teredo the shell is " globular, open in front 

 and behind, lodged at the inner extremity of a burrow partly 



Fig. 381. ParapJiolas mersa, viewed from one side and above. Cretaceous. 

 (After Stoliczka.) 



or entirely lined by shell ; valves three-lobed, concentrically 

 striated, and with one transverse furrow ; hinge-margins rer 

 tiected in front, marked by the anterior muscular impres- 

 sions ; umbonal cavity with a long curved muscular process " 

 (Woodward). Species of Teredo occasionally reach a very 

 large size, and they are known in the fossil state both by 

 their shells and by their burrows in wood. The genus seems 

 to have commenced in the Lias, and is well represented at 

 the present day. The Devonian genus Cimitaria is probably 

 referable to this family, in which case it is the oldest repre- 

 sentative of the group. 



END OF THE FIRST VOLUME. 



