218 
SILURIA. 
[Chap. X. 
rites pyriformis, Sil. Syst.), Foss. 19. f. 4, 5, and the var. H. megastoma, M'Coy (?), 
f. 3, H. tubulatus, f. 1, and Plasmopora petaliformis, f. 2. Besides these, there 
is the doubtful fossil, Stromatopora striatella, Foss. 52, usually arranged with 
the Corals, and much resembling them. Its true position is uncertain ; it may 
even belong to the tribe of Sponges. 
Fossils (52). Upper Silurian Stromatopora. 
A section of Stromatopora 
striatella, d'Orb. (St. concen- 
trica, Sil. Syst.). A very com- 
mon fossil in the Wenlock 
Limestone. 
In addition to those just quoted, several of the conspicuous Corals of the Upper 
Silurian strata have already been enumerated, pp. 119, 120. Of the latter it 
may be truly said that they swarm in the Wenlock Limestone, are found in 
diminished numbers in the Aymestry rock, and are much less plentiful in the 
muddy sediments of the Wenlock Shale and Lower Ludlow rock. 
Of the prominent species, Favosites alveolaris and F. Gotlandicus are, perhaps, 
the most generally diffused, and occur in masses varying from the size of a hazel- 
nut to two or three feet in diameter. The former may easily be distinguished 
(p. 119, Foss. 18. f. 4) on breaking the mass, by the angles of the tubes being 
toothed, while those of the other, F. Gotlandicus (f. 2, 3) are smooth-edged re- 
gular prisms, on which the double row of pores is very conspicuous. F. cristatus, 
f. 1, is almost as frequently met with, and forms whole strata on the coast of the 
Dingle promontory in Ireland. All the three species range, indeed, up to, but 
not into, the Devonian period *, and are widely distributed over the Northern 
hemisphere. The various forms of Favosites fibrosus, Goldf., are not less com- 
mon ; but this latter fossil does not appear to be so abundant in the Upper as in 
the Lower Silurian, or to assume so many variations in form. It is globular, 
lobed, or branched ; and on the slabs of limestone at Dudley there very com- 
monly occurs a narrow branched variety, with numerous small pores intermixed 
with larger ones. This form is very curious, and is figured in my larger work 
(Sil. Syst. pi. 15 bis, f. 9)f as a variety of Favosites spongites, Goldf. Professor 
Milne-Edwards believes it to be of a different genus, and has named it Ckeetetes 
Fletcheri, in honour of a gentleman who has long been a judicious collector of 
the Dudley fossils. 
The species called Favosites oculatus, Foss. 18. f. 6, is very abundant in the 
Wenlock limestone ; but it is very doubtful if it be a Coral : it is named Alveo- 
lites repens in the work of Milne-Edwards and Haime j but it is probably a 
Polyzoon, and belongs to Ceriopora. 
Next in importance to the Favosites are the large species of the genus Helio- 
lites. Of these, the most common, IT. interstinctus, Foss. 19. f. 3, 4, 5, occurs 
either in globular and pear-shaped masses, or of a flat discoid form, or as a thin 
incrusting expansion over other Corals and Shells. , 
Alveolites Labechii, M.-Edw., a Coral two or three inches broad, which looks 
* It is right to state that M. Milne-Edwards the Wenlock and Ludlow rocks, I must refer the 
distinguishes all the Devonian from the Silurian reader to the ' Silurian System,' and the faithful 
Corals. and able descriptions by Mr. Lonsdale. The plates 
t For a further acquaintance with the Corals of of Corals in that work are reproduced here. 
