AQUATIC ANIMALS OF THE COAL. 



205 



beaks more central, than No. 1. It occurs in a bed of sliale at the 

 base of the Middle Coal scries at the Joggins. 



(4.) Naiadites arenacea (Dn.) — Fig. 45. — Elliptical ; twice as long 

 as wide ; beaks prominent, one-fourth from anterior end, which is 

 compressed and rounded. In the Upper Coal formation at Pictou. 



(5.) Naiadites ovalis (Dn.) — Similar in general form to No. 4, but 

 much broader in proportion. See paper above cited, Fig. 24. It 

 occurs in bituminous limestone, with cyprids, in the lower part of the 

 Joggins Coal measures. 



(6.) Naiadites angidata (Dn.) — Fig. 46. — Similar in general form 

 and proportions to No. 4, but with more prominent beaks, a straight 

 hinge-line, and an undefined ridge running backward from the umbo, 

 and causing the posterior extremity to present an angular outline. 

 Lower Coal formation at Parrsborough. 



(7.) N. obtusa (Dn.) — As large as N. carhonaria^ but remarkable 

 for the broad and truncated form of its anterior end, giving it an 

 approach to a quadrangular form. It is thin, and much marked by 

 growth lines. Lower Coal measures, M'Lellau's Brook, Pictou. 



II. Si^irorhis carbonarius. — Fig. 47. — This little shell, which I de- 

 scribed as a Spirorbis as long ago as 1845,* is apparently not specifi- 

 cally distinct from Microconchus carbonarius of the British Coal-fields. 



Fig. 47. — Spirorbis carlonarius ; not. size attached to Cordaites, and magnified. 



Its microscopic structure is identical with that of modern Spirorbes^ 

 and shows that it is a true worm-shell. It is found throughout the 

 Coal formation, attached to plants and to shells of Naiadites, and must 

 have been an inhabitant of enclosed lagoons and estuaries. Its occur- 

 rence on Sigillarice has been used as an argument in favour of the 

 opinion that these trees grcAV in sea-water ; but, unfortunately for 

 that conclusion, the Spirorbis is often found on the inside of the 

 bark, showing that this had become dead and hollow. Beside this, 

 the same kind of evidence would prove that Lepidodendra, Cordaites, 



* Quart. Jouni. Geol. Soc., vol. i. p. ^'2(\. 



