Freside'fifs Address. 51 



Coal and Iron series. I believe there is an undescribed one 

 from the latter series of the Bo'ness coalfield, but I was never 

 able to obtain other than crushed examples. 



Of the Arcidse but one genus is met with in the Carboni- 

 ferous rocks of Scotland, Area itself, comprising about five 

 species. They do not call for detailed notice, but one fact 

 may be referred to — the preponderance of Belgian species,* 

 as against those of more purely British type. American 

 Palaeontologists now employ -|- the Jurassic genus Maerodon 

 (Lycett) for the reception of their arciniform shells of the 

 Carboniferous period. After examining the hinges of some 

 European, as well as strictly British species, I think there 

 may possibly be grounds for this, without, however, expressing 

 a decided opinion. 



The pretty and compact genus Nueida is the only Carboni- 

 ferous member of the Nueulidm we appear to possess. It is 

 one of the richest in species after Aviculopecten, and contains 

 several very interesting forms with regard to the morphology 

 of the genus. The late Mr J. W. Salter proposed J the 

 transfer of the Carboniferous Nucidas with the next genus 

 Niteulana to his Ctenodonta, a group of Silurian shells with 

 the characters of Niicida, but without a cartilage pit. Pro- 

 fessor M'Coy, however, has described § this important feature 

 in the Carboniferous type of the genus, N. gibbosa (Fleming), 

 but I do not know that a cartilage pit, accompanied by the 

 usual hinge teeth, has been observed in any other species 

 found in our Carboniferous rocks. The presence of Cteno- 

 donta proper (or as it should perhaps be called Tellinomya, 

 Hall) has yet to be proved in the latter. The Nuculidse 

 form a convenient family, distinguished from the following, 

 or Nuculanidee, by their much shorter form posteriorly, and 

 entire pallial impression.il 



Nuculana, the representative genus of the family Nucu- 

 lanidce almost equals its ally Niieida in the number of species 



* Armstrong and Young, Cat. W. Scot. Foss. , p. 53. 

 + Miller, Cat. American Pal. Foss., p. 194. 



% Mems. Geol. Survey, 1866, iii., p. 345 ; Iron Ores of Great Britain, pt. 

 3, 1861, p. 221. 



§ Brit. Pal. Foss., p. 512. 



II Stoliczka, Mem. Geol. Survey, India, iii., p. 325. 



