ANNELIDA— TUBICOLA. 



237 



10. S. rotula Morton. Cretacic. 

 Large (9 mm. in diameter), discoid, bicarinate ; coiling dextral 



or sinistral ; aperture subcircular, but section of tube quadrangular. 

 Jerseyan (Vincentown) of New Jersey. 



11. S. calvertensis Martin. (Fig. 152 1.) Miocenic. 



Fig. 1520. Spirorbis ant/wacosia, much 

 enlarged. (After Whitfield. ) 



Fig. 1521. Spirorbis calvertensis, 

 attached to shell, enlarged. (Mary- 

 land Survey. ) 



Small (diameter 1.3 mm.) tubes attached by flat under sides to 

 molluscan shells ; surface with indistinct, somewhat irregular annu- 

 lations ; coils somewhat sharply ridged on top. 



Miocenic of Maryland (Calvert formation), etc. 



III. CONCHICOLITES NicllolsOU. 



Growing in clusters, attached to orthoceran and brachiopod 

 shells, etc., by small, lower end. Tubes conical, slightly bent, thin- 

 walled, made up of numerous short rings, each partly overlapping 

 the preceding one; structure non-vesicular. Ordovicic. 

 12. C. corrugatus Nicholson. (Fig. 1522.) Ordovicic. 



Fig. 



1522. Conchicoliles corrugatus, a group of individuals attached to shell and 

 rock, X i> and a single one enlarged. (After Hall and Clarke.) 



