36 CONTRIBUTIONS 



the Eocene period. In this country Dr Morton has observed 

 casts in the Upper Green Sand of New Jersey and Dela- 

 ware, and Mr Say one species, the attenuatum, in the 

 Tertiary of Maryland. 



FAMILY SERPULEA. 



GENUS SPIRORBIS. Lamarck. 



S. tubanella. Plate 1. Pig. 4. 



Description. Shell discoidal, concave in the centre, sub- 

 carinate above; whorls about three, contiguous ; aperture 

 round and enlarged. 



Diara. less than l-10th of an inch. 



Observations. This minute species was found attached 

 to the inner side of the valve of a Plicatula. Of eleven spe- 

 cimens thus attached, eight are sinistral and three dextral. 



I am not aware of this species having been observed in 

 Great Britain. Lamarck describes one species from Grig- 

 non. It has not, I believe, before been observed in the 

 strata of this country. 



