DESCRIPTION OF THE FOSSILS. 217 
septa in the lower valve divide it into three parts as in pentamerus, to which by this 
insufficient character it would be referred. Many spiriferaj exhibit, less distinctly, the 
same phenomenon. 
S. distans. Sow. not figured. Bolland ; Dublin. 
Resembles Sp. semicircularis, (fig. 15,) in shape, hut its mesial fold is not sulcated 
on the upper valve, (in some of my specimens it is not sulcated on either valve.) I lie 
cardinal area is wider than even the variety a- of S. semicircularis, (fig. 15.) It is 
more gibbous than that shell and has a wider frontal wave. 
B. Angustatce. Cardinal line as wide as the shell; valves with in- 
curved beaks. Mesial fold defined between two deeper furrows on the 
upper valve. 
S. semicircularis. Ph. PL IX. fig. (15,16.) Chipping; Whitewell ; 
Queen’s County, Ireland ; Isle of Man. 
Cardinal area variable ; upper valve very nearly semicircular ; surface covered by 
radiating smooth sulci and ribs which are entire or divaricate near their origin ; mesial 
fold sulcated. «. Cardinal angles right. (3. Cardinal angles acute. (Differs from 
Sp. distans by the sulcated mesial fold, and is more depressed.) 
S. striata. Sow. t. 270. Bolland ; Derbyshire ; Ireland. 
It is difficult to distinguish this species from Sp. semicircularis and its congeners. 
The cardinal extremities are rounded or obtusely angulated; the cardinal area is 
concave with subparallel sides ; the radiating ribs are small and often divided ; the 
upper valve projects from the circular curve in the middle. 
S. convoluta. Ph. PI. IX. fig. 7- Bolland. 
Width four times the length ; cardinal area concave ; surface obtusely and un- 
equally radiated. 
S. rhomboidea. Ph. PI. IX. fig. 8, 9. Bolland ; Ireland. 
Width fully double the length, extremities subcylindrical ; cardinal area very 
wide, mesial fold defined; surface radiated with obtuse smooth sulci. The great 
proportionate width of the cardinal area is a strong character, yet it very much 
resembles both Sp. convoluta, Ph. and Sp. attenuata, S. In figure it agrees with 
Sp. triangularis, Sow. t. 562, but the ribs of that species are bolder, and its mesial fold 
is different. 
S. fusiformis. J. De C. Sow. PI. IX. fig. 10, 11. Bolland. 
Mesial fold indefined; surface finely radiated, cardinal area large, hollow. (The 
name is given by Mr. J. De C. Sowerby.) 
S. triangularis. Sow. PL IX. fig. 12. Bolland ; Kirby Lonsdale ; 
Derbyshire. 
