lxii DESCRIPTIVE REMARKS. 
rocks, This class of the Mollusca are with the Actinozoa or Corals the 
most abundant and typical of all the fossils of these rocks, and especially 
of the Middle Devonian series. 
Some of the purely Devonian species are figured on Pl. xxx., 
amongst them Stringocephalus Burtini, fig. 4, a, b, a remarkable shell, 
having a very prominent beak ; Spirifera disjuncta, fig. 6, a very 
abundant species in the Middle and Upper Devonian of N. and 8. Devon 
and Cornwall, although apparently not very distinct from some of the 
varieties of S. striata of the Carboniferous rocks, Cyrtina heteroclita, 
fig. 7, a, 6, a sub-genus of Spirifera, according to Woodward, having 
a very prominent beak. <Atrypa desquamata, fig. 9, is a frequent 
fossil, especially in the Middle Devonian, occurring also in the Upper 
or Petherwin group, and allied to the common Silurian species Atrypa 
reticularis, which is also not uncommon in Devonian strata. Penta- 
merus brevirostris, fig. 11, belongs to a genus which attained its 
maximum in Upper Silurian rocks; a shell remarkable for its five di- 
visions (from which its generic name is derived), caused by the dental 
and septal plates attached to each valve; and Chonetes Hardrensis, fig. 
14, a small flattened shell having the hinge margin of the ventral 
valve provided with a series of tubular spines. This shell occurs in 
Middle and Upper Devonian, continuing on into Carboniferous strata. 
The Devonian Concuirera (bivalve shells), or Lamellibranchiata, 
according to Mr. Etheridge’s able summary in the Journal of the Geo- 
logical Society (before quoted), p. 678, comprises twenty-eight genera, 
including fifty-eight species; of these five genera, including seven 
species only, continue into the Carboniferous series. Some of the most 
characteristic of these are figured on Pl. xxxi., viz., Aviculopecten 
transversus, fig. 1. Avicula Damnoniensis, fig. 2, and Cucullea Har- 
dingti, fig. 8, all Upper Devonian species, the two latter being abundant 
in the sandy strata of that division in the Barnstaple series. Both of 
these bivalve shells are also found plentifully in the ‘“‘ Coomhola” grits 
and shales of the Lower Carboniferous strata in the county of Cork.* 
The remarkable shell I/egalodon cucullatus, fig. 4, a, b, is a typical 
Middle Devonian species having an enormous development of the hinge 
teeth, a characteristic fossil in the limestone of the 'lorquay and Llfra- 
combe series, also occurring in the Lynton group of the Lower De- 
vonian. The large freshwater bivalve Anodonta Jukesii, fig. 5, (ante 
p. lv.), has hitherto only been observed in the Upper Old Red Sandstone 
of Ireland, in the counties of Kilkenny, Cork, and Waterford. 
Of the Gastrropopa (Univalves), forty-seven species are included 
in Mr. Etheridge’s list, two only of these occur in the Lower Devonian, 
the Lynton group; thirty-seven occur in the Middle Devonian (Tor- 
quay group), and four only of these in the Ilfracombe group, also 
Middle Devonian. In the Upper Devonian nine species occur in the 
Petherwin group, three in the Baggy, and nine in the Pilton groups, 
three of the latter continuing into this group from the Middle De- 
* Explanation to Map 187, &c., Geol. Survey Ireland, pp. 16, 17, & 28. 
