506 W. J. SOLLAS ON THE SILURIAN DISTRICT 
EXPLANATION OF PLATE XXIV. 
Figs. 1 & la. Cycloncema turbinatum, sp. n. Ludlow, Cae Castell, Rhymney 
river. Natural size. 
2. Modiolopsis inflata, M‘Coy, var. elevata, Soll. Natural cast of right 
valve. ‘Ctenodonta”-bed, Wenlock, Rhymney Quarry. Nat. size. 
3&3. Orthonotus navicula, sp. n. Ludlow, picked up near Cross Dow- 
ton, Rhymney. Nat. size. 
4. Holopella hydropica, sp.n. ‘ Ctenodonta’’-bed, Wenlock, Rhymney 
Quarry. Nat. size. 
5. Holopella gracilis, sp.n. ‘“ Ctenodonta”’-bed, Rhymney Quarry. Nat. 
size. 
6. Holopella minuta, sp.n. ‘ Ctenodonta”-bed, Rhymney Quarry. Nat. 
size. 
7. Leda(?) ambigua, sp.n. Ludlow, Cae Castell, Rhymney river. Nat. 
size. 
8. Murchisonia elegans, sp.n. ‘‘ Ctenodonta”-bed, Rhymney Quarry. 
Nat. size. 
9. Ambonychia (?) tumida, sp. n. Lower Wenlock, Pen-y-lan Quarry. 
Nat. size. 
10 & 10a. Cyclonema simplex, sp.n. Wenlock limestone, Cae Castell, 
Rhymney river. 10a. Exterior of a part of the body-whorl to 
show the ornamentation. Nat. size. 
11. Murchisonia corpulenta, sp. n. Wenlock limestone, Cae Castell, 
Rhymney river. Nat. size. 
- 12. Oolitic granules contained in a cell of Favosites fibrosus. a,a. The 
containing cell-wall. Wenlock limestone, Cae Castell, Rhy mney. 
Transv. sect. (X 30.) 
13. Granule of black iron oxide (a), containing an angular fragment of 
glauconite (b). Transy. sect. Wenlock limestone, Cae Castell, 
Rhymney. (x 30.) 
14, Glauconite cast of a Foraminifer dissolved out from the bed of lime- 
stone occurring just above the Khymmey grit in the Cae Castell 
section. (xX 30.) 
15. Cyclonema angulatwm, sp. n. Lower Wenlock, Pen-y-lan Quarry. 
Nat. size. 
16. Ellipsoidal granule of granular calcite surrounded by a film of black 
iron oxide. Tang..sect. Wenlock limestone. (x 30 
17. Two oolitic granules which have become jomed together in the last 
stages of growth. Transy. sect. Wenlock limestone. (x 30.) 
18 & 19. Oolitic grains in the cells of Favosizes fbrosus, showing medifica- 
tion of spherical form produced by adaptation during growth, 
Transv. sect. Wenlock limestone. (x 30.) 
20. Oolitic grain with deeply infiected margin, lying in the centre of a cell of 
Ff. fibrosus. Transy. sect. W. enlock limestone. (x 30.) 
21 & 22. Modiolopsis acutizrora, sp.n. 21, natural cast of the extericr ; 
22, of the interior, of the left valve. ‘‘ Cienodonta”-bed, Wenlock, 
Rhymney Quarry. Nat. size. : 
23. An Alga from Ludlow beds, Cae Castell, Rhymney. (x 2.) 
24, Ferruginous grain from W enlock lim 1estone, Cae Castell. a. External 
layer of sranules suspended in the surrounding matrix of clear 
calcite. b. Zone of black iron oxide. ¢c. Zone of brownish-red 
opaque ferruginous material. d. Zone of transparent brownish 
calcite. f. White opaque nucleus. Transy. sect. (x 38 
25. Ferruginous grain from Wenlock limestone, Cae Castell, having the 
form of an Entomostracan valve. @. Black iron oxide surrounding 
the granule and forming more or less concentric rings within it. 
This structure may result, from the infiltration of an oolitie grain by 
iron-oxide. Transy. sect. (x 30.) 
26. Elliptical ring of clear calcite, surrounded by brown opaque matrix 
and enclosing sand grains cemented by ferruginous matter. Similar 
