746 SYSTEMATIC PALEONTOLOGY 



The genus has been reported from strata as early as the Silurian. In 

 the Purbeck beds of northwest Germany one member of the genus Serpula 

 attains considerable importance as a rock-builder. Eecent Serpulce are 

 world-wide in distribution. 



The classification of the fossil annelids is of necessity in a lamentable 

 state, since only the most superficial characters are available for determin- 

 ing the identity of species. In many cases it is impossible to tell whether 

 the tube in question was secreted by a worm or a mollusc, although, as a 

 rule, the latter can be isolated by the presence of internal septse and of 

 only two instead of three constituent layers of shell substance. However, 

 it is highly probable that a large number of tubes have been referred to 

 this group which are properly referable to the tube-secreting univalves. 



A. Tubes free; subcircular in cross-section Serpula whitfieldi 



B. Tubes adherent; tubes triangular in cross-section Serpula trigonalis 



SERPULA WHITFIELUI Weller 



Diplpconcha (Serpulaf) cretacea ? Whitfield, 1892, Mon. U. S. Geol. Survey, 

 vol. xviii, p. 170, pi. xx, fig. 25. (Not Diploconcha cretacea Conrad.) 



Serpula whitfieldi Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 

 308, pi. xix, fig. 2. 



Description. " Tubes irregularly arcuate, slightly flexuose, increasing 

 in diameter very gradually; surface of shell lamellose where partially 

 exfoliated, in cross-section appearing to be made up of concentric lamellae. 

 The dimensions of the largest tube observed are : Total length 70 mm., 

 maximum diameter 6.5 mm." Weller, 1907. 



Type Locality. Crosswicks Creek, New Jersey. 



Occurrence. MONMOUTH FORMATION. Brightseat, Brooks estate near 

 Seat Pleasant, Prince George's County. 



Collections. Maryland Geological Survej^, Columbia University. 



Outside Distribution. Monmouth Formation. Navesink marl, New 

 Jersey. 



SERPULA TEIGOXALIS n. sp. 

 Plate XLVII, Fig. 15 



Description. Tubes of two layers, recumbent, contorted, adherent in 

 che type to the inner surface of a bivalve ; tapering from a fine cord to a 

 mere thread, cross-section slightly ovate, medial carina developed along 



