80 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



manner of the tail-joint of Slimonia (Pterygotus) acuminata. (See 

 Quart. Journ. Geol. Soc. vol. xii. p. 28.) 



There are no surface-markings nor marginal serrations. 



Locality. Coal-measures ; Joggins, Nova Scotia (cabinet of Dr. 

 Dawson). 



While dealing with Crustacea of the Carboniferous rocks, I may 

 be permitted to make a correction in reference to my last paper*, 

 and to alter the term Palceocrangon to Crangopsis. I had overlooked 

 the fact that the term " Palaeocrangon " was applied to the small 

 Isopod Crustacean in the Permian rocks described long ago by 

 Schauroth (see Quart. Journ. Geol. Soc. vol. xiii. p. 214). It is true 

 my correspondent, Mr. Kirkby, would replace that name by a more 

 satisfactory term, as Palaeocrangon suggests a wrong affinity. Most 

 naturalists, however, are agreed that a generic name once given is 

 entitled (like a specific one) to priority, unless utterly erroneous in 

 meaning, or accompanied by a manifestly imperfect description. 



Fossil Shells from the Coal-measures of Nova Scotia. 



I have added figures of three species of shells sent to me by 

 Dr. Dawson. They are from the Coal-measures, and are specially 

 interesting as being the genera common in our own Coal-deposits, 

 and which I cannot but regard as of marine origin. There are three 

 species, which I find Dr. Dawson has named respectively Naiadites 

 elongatus, N. carbonarius, and N. Icevis, in the Supplementary Chapter 

 to his ' Acadian Geology.' 



The first and last are species of a genus which I have described 

 and figured as Anthracomya in the Memoirs of the Geological 

 Survey f. They are thin equivalve shells, wider behind, and with a 

 (byssal ?) sinus on the anterior ventral edge. A wrinkled epidermis 

 shows that the animal probably had a closed mantle and respiratory 

 siphons; and the ligament is external, as in Panopcea, which is 

 essentially one of the Myadce. 



As Dr. Dawson had only proposed the name Naiadites without 

 description, perhaps these shells may be allowed to retain the name 

 I have given them. The Anthracomya (Naiadites) Icevis (fig. 2) is, I 

 believe, identical with a shell from the Upper Coal-measures of 

 Manchester. 



For the second species, however, N. carbonarius (fig. 3), no generic 

 name has yet been proposed, though Professor King had long ago 

 noticed the genus (Ann. and Mag. Nat. Hist. Jan. 1846, vol. viii.). 

 It includes the so-called Myalince. Nor can they be described as 

 species of Dreissena, as has been done by Herr Ludwig, in his recent 

 descriptions of Coal-fossils in the ' Palaeontographica,' vol. ix. 



Meantime, until Professor King or myself describe some of the 

 Coal-fossils of this group, I shall employ the name Anthracoptera 

 for these triangular shells. They are abundant in our Coals. 



* Quart. Journ. Geol. Soc. vol. xvii. p. 533. 

 f " Iron-ores," 1861, p. 229, pi. 2. 



