ANNELIDA— TUBICOLA. 235 



Order POLYCH^TA. 



Suborder Tubicola. 



I. Serpula Linne. 



Calcareous tubes, free or adherent, firm, irregularly contorted, 

 sometimes spirally enrolled and frequently clustered together in 

 large numbers. From the Jurassic onward, the usual condition is 

 attached to other fossils. Siluric ( ?)-Recent. 



1. S. whitfieldi Weller. Cretacic. 

 Tubes irregularly arcuate, slightly flexuous, gradually increasing 



in diameter; surface lamellose when exfoliated, in section concen- 

 trically lamellose. 



Ripleyan (Navesink and Crosswicks) of New Jersey. 



2. S. dianthus Verrill. Pleistocenic-Holocenic. 

 Singly adhering to shells, or growing in complex clusters, often 



making large masses ; tubes contorted, averaging 3 mm. in diameter. 



Abundant in Pleistocenic (Sankaty) beds of Nantucket, common 

 m modern fauna along the Atlantic coast. 



II. Spirorbis Daudin. 



Minute, snail-like or spirally enrolled calcareous tubes, cemented 

 by the flat under side; the spiral may be either dextral or sinistral 

 and is usually ornamented externally with concentric striae or 

 annulations, sometimes with tubercles or spines; living species 

 (marine) commonly adhering to sea weeds. Ordovicic-Recent. 



3. S. laxus Hall. (Fig. 15 17.) Siluric. 



Fig. 1517. Spirorbis laxus^ upper and lower side of a close coiled specimen ; and 

 two loosely coiled individuals. All greatly enlarged. (Pal. N. Y., III.) 



Coiled, sometimes in a close low spiral, but more often with the 

 last portion separated from the earliest whorls, or irregularly 

 twisted instead of coiled; whorls round, with sharp annulations. 



Manlius of New York; Lower Monroe (Raisin River) ,of 

 Michigan, Ohio, Canada, etc. 



