* 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. Fig. 4. 
Description. Shell discoidal, concave in the centre, sub- 
carinate above; whorls about three, contiguous ; aperture 
round and enlarged. 
Diam. less than 1-10th 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. 
