[MATTHEW] ORDOVICIAN SYSTEM ON THE ATLANTIC COAST 261 
the shell, or pseudo-platform are raised, and there is a median plate or 
septum. A band similar to a crescent goes around the back of the shell 
within the deltidial area, and connects a set of three lateral muscles. The 
arrangement of the muscle-scars, especially the centrals, is like that of 
Lingulella, of the laterals like Frimerella and the parietal bands have the 
position of those of Lingula. The notation used in describing the parts 
of this and of the following species, is that of Davidson and King for the 
Trimerellidæ. The type of the genus is Lingulella (?) afinis, Billings. 
LINGULOBOLUS., AFFINIS, Bill., sp., Pl. L., Figs. 4a and 0. 
Lingulella (2) affinis, Billings, Palæoz. Fossils, vol. ii., pt. i., p. 67, fig. 35. 
Mr. Billings’s description of this species is as follows : 
“Ventral valve elongate, conical, or acutely triangular. Apical 
angle 45°, Front margin gently convex in the middle, rounded at the 
angles; sides nearly straight, uniformly converging from the anterior 
angles to the back. Surface of very fine, longitudinal striæ, about ten in 
the width of a line. This species is founded on the single specimen of a 
ventral valve above figured. The upper two-thirds is partly worn away 
in the middle, leaving only the outline in the stone. It appears to have 
been, when perfect, gently convex, the rostral portion near the beak, 
semi-cylindrical. Length about thirteen lines, width nine lines. The 
dorsal valve has not been identified.” 
Among the specimens from Great Bell Island received from Mr. 
Howley are some examples of a large shell which, though it differs in its 
proporuons from Billings’s figure of L. ? affinis, I believe to be this species, 
for while he speaks of the apical angle as being 45°, it is actually as 
drawn, 55°. The type specimen is perhaps narrowed by pressure. The 
internal markings of the shell sent me by Mr. Howley are so well shown, 
that whether this shell is or is not LZ. ? affinis, it is worthy of description. 
These internal markings are as follows: 
In the dorsal valve the cardinal muscle is divided, and is close to the 
margin ; in front of this muscle on each side are the oval scars of a large 
pair of lateral muscles ; these scars have a pointed anterior lobe, and ex- 
tend forward to a point one-third of the length of the shell from the 
hinge-line ; in front of these scars is a faint, oval incurved impression 
(muscle scars ?) extending half way to the front of the valve ; these form 
on each side of the valve the anterior end of the crescent. The central 
muscles form a group of scars just behind the middle of the valve ; there 
are two large laterals and a group of smal] central muscles about as 
distant from the laterals as these are from each other: the small central 
group is resolvable into four little scars; the two posterior ontiguous 
and parallel; the two anterior approximate, but spreading anteriorly. A 
