NODOSARINiE. 63 



the Arctic circle to the equator. It occurs in many sandy shore-deposits ; but its 

 favorite habitat is mud at 50 — 100 fathoms, and is continually met with in the 

 deepest soundings, although never abundant there, and generally small. 



Dentalina communis, D'Orhigny. 



Sub-variety — D. pauperata, D'Orb. (see above, p. 59). 



Characters. — Shell elongate, sub-cylindrical, composed of many chambers. The 

 early chambers sometimes cylindrical, the others more or less ventricose. Shell often 

 irregular and unsymmetrical. Length ^^th to ^th inch. 



Dentalina pauperata is a mere name of convenience for certain forms of Dentalina 

 communis, in which the chambers have a compact style of growth, the septal lines being 

 sometimes quite obscured. Large specimens were not uncommon in the Crag beds at 

 Sutton worked by Mr. S. Wood. 



We find D. pauperata in marls of the Lias, in the Chalk, in the various fossihferous 

 Tertiary clays, and occasionaUy recent where other Dentalina abound. 



Dentalina communis, D'Orbipiy. 



Sub-variety — D. brevis, D'Orb. (see above, p. 59). 



Characters. — Shell stout, sub-cylindrical, consisting of few (three to five) rather 

 ventricose and more or less compact chambers. Length i^^th inch. 



Of the poorly grown specimens of unstriated Dentalina (or curved Nodosaria radicula), 

 the stunted few-chambered forms may be conveniently taken together under D'Orbigny's 

 designation D. brevis. The characters are of little interest or significance, and it is so 

 associated in distribution with the sub-typical D. communis as not to require separate 

 treatment. Our figured specimen is from the BridHngton Crag. 



Subyenus — Vaginulina, D' Orbigny. 



Orthoceras, d-ualtier, Baisch, Hanley. 



Nautilus, Linni, Martini, Schroeter, Gmelin, Montagu, Turton, Mafon and Rackett, 

 Dillwyn, W. Wood. 



