New Species of Trildbite, 41 



In the aggregates thus exhibited, there is an apparent want 

 of conformity in the relative proportions of each class. This 

 wholly arises from the extinct genera of the ancient strata ; for, 

 on making the comparison between the recent series and those 

 of the latest group of deposits, no such difference will be per- 

 ceived. On the contrary, a considerable agreement between 

 the proportions of existing species and the several classes of 

 fossil shells in the tertiary beds prevails ; the average increase 

 of numbers being about sevenfold. 



If we follow the investigation further, we may observe that 

 the fossil multilocular and complicated Testacea, which charac- 

 terise the oldest formations, and decidedly preponderate in 

 that end of the series, form one fifth part of the entire cata- 

 logue; but, amongst the recent shells, this class constitutes less 

 than a fortieth part, and in the tertiary series only a fiftieth 

 part. 



The conclusion to be drawn from a summary of facts more 

 numerous, and on a more extended scale than, until recently, 

 has been attainable in this department of natural history, is, 

 that in proportion as we descend the vast series of deposits 

 that overspread this portion of the earth, so do we recede, 

 step by step, from the circle of existing organised beings, and 

 from the phenomena attendant on their structure, their habits, 

 and their adaptations. 



R. C. T. 

 February, 1829. 



Art. VIII. An Account of a neiv Species of Trilobite, found in 

 the Barr Limestone in the Neighbourhood of Birmingham. By 

 Frederick Jukes, Esq. With a Note by J. D. C. Sowerby, 

 Esq. «., 



Sir, ' 



Allow me to present to you the enclosed drawings of a 

 curious fossil {Jigs. 8, 9, 10.), discovered in the lime quarries at 

 Hay Head, near Great Barr, a village about nine miles from 

 this town. It appears to be of the Trilobite kind, retaining a 

 considerable quantity of a fine crustaceous covering of a dark 

 brown colour, and highly polished. The drawings represent its 

 exact size, measuring in length about 5 in., and in width S\ in., 

 being much larger than fossils of that character usually found 

 in this country. The Trilobites already discovered in the 

 Dudley lime formation are of two kinds ; viz. one which is 

 commonly called the Dudley fossil (Jg. 1 1 .), and mentioned in 

 Parkinson's work upon Organic Rernains, and another (Jig. 



