CHAPTER IV. 



Branch VERMES. 



Class ANNELIDA. 



Sub-Class CHAETOPODA. 

 Order POLYCHAETA. 



Sub-order TUBICOLA. 

 Genus SSRPULA Linneus. 



Serpula circularis n. sp. 

 Plate XIX., Figs. 5-6. 



Description. Tube rather large, moderately thick, increasing 

 gradually in size, the increase being more rapid as it approaches 

 the aperture, not closely coiled, the first volution of the type 

 specimen forming a rather large irregular circle, after which the 

 shell is in contact for about one-fourth volution nearly to the 

 aperture. Another specimen is perhaps not in contact at all. 

 Aperture more or less subcircular or subelliptical in outline. The 

 surface of the shell is marked by more or less irregular, annular 

 lines of growth. 



The dimensions of the type species are: greatest diameter -of 

 aperture 8 mm.; length of tube, 72 mm.; greatest diameter of 

 space within first volution, 13 mm. 



Remarks. The type specimen is the only individual observed 

 which is anywhere near complete, though other fragments indi- 

 cate that the large open coiling of the tube was a common habit 

 of growth. The type has apparently been attached to some large 

 shell, probably a Gryphaea, during life, by the flatter side, al- 

 though in its present condition it is free. 



Formation and locality. Marshalltown clay-marl. Near 

 Swedesboro (177). 



Geographic distribution. New Jersey. 



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