TRANSACTIONS OF SECTION C, 787 
Ostracoda. 
The Ostracoda also give us definite forms peculiar to the early Cambrian beds. 
Such are the types represented in Beyrichona and Hipponicharion; such also are 
those with flexible tests represented by Aluta. Other Ostracoda are present in 
more varied forms than in the Paradoxides beds. 
To sum up these distinctive features of the animals of the earliest Cambrian 
faunas, we may say— 
1. That the Trilobites retain larval characteristics to an unusual degree. 
2. The Brachiopoda have a large percentage of Obolide. 
3. The Ostracoda are plentiful and varied, and present some peculiar types. 
3. Report on Life Zones in British Carboniferous Rocks. 
See Reports, p. 415. 
4. The Range of Species in the Carboniferous Limestone of North Wales. 
By G. H. Morton, £.G.8. 
Attention having recently been directed to this subject, I have been induced 
to present the results of many years’ collecting in the Carboniferous Limestone of 
North Wales. The formation there presents four well-defined subdivisions, each 
of them, with the exception of the highest, having distinct lithological characters, 
viz.—Lower Brown Limestone, Middle White Limestone, Upper Grey Limestone, 
and the Upper Black Limestone. Lists of the fossils have been made, collected 
more or less continuously along the country from each subdivision. 
In North Wales the occurrence and succession of the species in the subdivisions 
vary in different areas, and the Jarger the area examined the more difficult it 
becomes to find species peculiar to certain horizons, In order to obtain a definite 
result, I have compiled three separate lists of the species vbtained in that number 
of distinct areas. There are the Llangollen, the Flintshire, and the Vale of 
Clwyd Lists. Each of the lists shows the relative scarcity and abundance, and the 
range of the species in the subdivisions; and although future search will doubtless 
add to the rare and occasional species, the number and range of the common 
and very common must be very nearly correct. Neither the rare nor the occa- 
sional species are of much use in defining distinct horizons in consequence of 
their rarity, and it is only the common and very common species that can be 
expected to indicate a definite horizon or zone. In North Wales a great difficulty 
arises from the occurrence of all the common and very common species in the 
Upper Grey Limestone, with the exception of Productus comoides, and although 
all pass downwards, they become scarce in consequence of the general paucity of 
fossils in the inferior subdivisions. 
In the Llangollen List there are 69 rare, 28 occasional, 16 common, and 27 very 
common species. Deducting Foraminifera, which are not in the other lists, there 
are 36 species that are common and very common, and they all occur in the Upper 
Grey Limestone, with the exception of Posidonomya Gibsoni from higher strata, 
and Productus comoides in the Lower Brown Limestone, all the other species in 
the list being rare and occasional forms. 
In the Flintshire List there are 92 rare, 35 occasional, 30 common, and 1? 
very common species, and of the 41 common and very common, 87 species occur 
_ in the Upper Grey Limestone, 4 of the remaining species, Posidonomya Becheri, 
Aviculopecten granosus, and A. papyraceus occurring in the Upper Black Lime- 
stone, and Productus comoides in the Lower Brown Limestone. 
In the Vale of Clwyd List, which includes the Great Orme’s Head, there are 
16 rare, 22 occasional, 12 common, and 10 very common species; and of the 
22 common and very common, 21 species occur in the Upper Grey Limestone, the 
exceptional species being Productus comoides. None of the 21 species are peculiar 
