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CHAP. VI.
PALÆOZOIC STRATA.
141
| Western Districts. | Eastern Districts. | Total Number of Species in each Class. | ||||||||||||
| Car- digan. |
Mar- loes. |
Fresh- water. |
Haver- fordwest. |
Carmar- then. |
Llan- deillo. |
Builth. | Usk. | Tort- worth. |
May- hill. |
Wool- hope. |
Abber- ley. |
Mal- vern. | ||
| Annelida | 4 | 2 | 1 | 2 | — | 3 | 3 | 3 | 3 | 2 | 4 | 5 | 9 | 13 |
| Crustacea | — | 9 | 3 | 16 | 1 | 24 | 4 | 10 | 3 | 3 | 9 | 6 | 14 | 28 |
| Cephalopoda | — | 3 | 2 | 2 | — | 16 | 4 | 10 | 3 | 3 | 9 | 6 | 14 | 28 |
| Heteropoda | — | 5 | 2 | — | — | 4 | 4 | 3 | 2 | — | 3 | 4 | 6 | 10 |
| Pteropoda | — | 1 | — | 1 | — | 2 | 1 | 1 | — | — | 1 | 2 | 2 | 3 |
| Gasteropoda | — | 11 | 6 | 1 | — | 21 | 5 | 13 | 6 | 7 | 13 | 4 | 26 | 44 |
| Lamellibranchiata | — | 12 | 7 | 1 | 1 | 30 | 6 | 24 | 1 | 9 | 18 | 12 | 25 | 45 |
| Brachiopoda | — | 19 | 6 | 24 | 1 | 61 | 28 | 34 | 8 | 32 | 51 | 40 | 63 | 97 |
| Echinodermata | — | 2 | — | 8 | — | 2 | — | 2 | 1 | 1 | 2 | 1 | 4 | 15 |
| Polypiaria | 1 | 17 | 2 | 18 | 1 | 23 | 12 | 26 | 1 | 19 | 34 | 22 | 29 | 53 |
| Number of distinct species in each districts. | 5 | 81 | 29 | 73 | 4 | 187 | 72 | 128 | 30 | 76 | 143 | 107 | 195 | |
If, taking the same 353 species, we inquire into their distribution through the strata of the eastern region (in which deposits are most sharply defined and present the greatest variety of mineral composition) we have the following table:—
| Anne- lida |
Crus- tacea |
Cepha- lopoda |
Hete- ropoda |
Ptero- poda |
Gaste- ropoda |
Lamelli- branchiata |
Brachio- poda |
Echino- dermata |
Polyp- iaria |
Number of distinct species in each districts. | |
| Dowston sandstone | — | — | — | — | — | — | — | 1 | — | — | 1 |
| Upper Ludlow | 7 | 10 | 12 | 4 | 2 | 16 | 19 | 20 | 1 | 5 | 96 |
| Aymestry rock | — | 6 | 5 | 2 | — | 11 | 12 | 28 | — | 14 | 78 |
| Lower Ludlow | 1 | 6 | 3 | — | 2 | 4 | 9 | 27 | — | 16 | 68 |
| Wenlock limestone | 2 | 11 | 7 | 2 | 1 | 4 | 9 | 38 | 2 | 40 | 116 |
| Wenlock shale | 3 | 8 | 2 | 1 | — | 5 | 12 | 32 | 1 | 11 | 75 |
| Woolhope limestone | 1 | 2 | 1 | — | — | 1 | — | 20 | — | 4 | 29 |
| Caradoc (Upper) | 2 or 3 | 4 | 1 | 3 | — | 10 | 1 | 29 | 2 | 13 | 66 |
| Caradoc (lower) | 1 | — | 2 | 1 | — | 2 | 3 | 3 | — | — | 12 |
| Trap | — | — | — | — | — | — | — | — | — | — | — |
| Black shale | — | 4 | — | — | — | — | — | — | — | — | 4 |
| Lowest sandstone | — | — | — | — | — | — | — | — | — | — | — |
The maximum of variety appears in the Wenlock
