Foraminifera from the North Sea, etc. 389 



grows ill length the spicules are absorbed and built into the wall 

 of the tube, other spicules being collected to serve in their place. 



Marsipclla cylindrka, although a neat builder, does not show 

 the skill and constructive ingenuity of its relative, M. spiralis. 

 Sponge spicules enter largely but not entirely into its construction, 

 being mixed indiscriminately with some sand-grains, mica, etc., in 

 varying proportions. Individual specimens vary greatly in the 

 neatness of their construction, some showing a slight tendency 

 towards a spiral arrangement of the fragments. We figure one 

 fragment in which this spiral twist is strikingly manifest. The 

 absence of the cement which characterizes M. sjnralis proves that 

 the fragment should be referred to M. cylindrica and not to M. 

 spiralis. Moreover the spiral is right-handed. 



The question might arise wliether the presence of the terminal 

 club-shaped head in Marsipella cijlindrica does not necessitate the 

 transference of the species to a separate genus. In view of the fact 

 that the terminal portion is so loosely constructed that it cannot 

 be said to close the tube, we see no reason at present for the transfer 

 of the species. We would, however, suggest that Norman's defini- 

 tion of his genus Marsipclla, now quoted,* should be amplified by 

 the inclusion of the words we have inserted in italics. 



* Norman, A. M., " On the Genus Haliphysema, with description of several 

 forms apparently allied to it." Ann. Mag. Nat. Hist., ser. 5, i. p. 281. 



Genus Marsipella n. g. 

 (/jLapirtiros, a purse.) 



" Test elongated, fusiform (or cylindrical) centrally cylindrical and drawn out 

 to gradually attenuated extremities, open at both ends {or closed anteriorly hij a 

 loosely aggregated knoh of spicules) monothalamous ; anterior extremity much 

 produced into a narrow contracted mouth-opening. Extraneous matter of body- 

 wall consisting for the most part of sand-grains, but at the oral extremity com- 

 posed almost solely of fragments of sponge-spicules longitudinally arranged." 



