480 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



and he liberally presented it to me. I forwarded this specimen to Sir 

 Philip Egerton, who states, that it most nearly resembles the curious 

 genus Nothosomus, but it is too imperfect to warrant any decided 

 opinion upon the subject, as the tail and dorsal fin are deficient. He 

 is inclined to think that it will ultimately prove to be a new genus. 



The position of the strata containing Insects at Ridgway near 

 Weymouth is not exactly the same as at Durdlestone Bay (Nos. 103 

 to 119, Mr. Austen's List), though it agrees pretty nearly with the 

 latter. In the neighbourhood of Dorchester they are somewhat 

 harder, but the prevailing colour is much the same, and no insect 

 remains have as yet been observed thei'e higher than the lower 

 Purbecks. 



Observations on the Organic Remains. 



No Archceoniscus has yet been met vdth at Durdlestone Bay higher 

 (I believe) than No. 58 in Mr. Austen's list of the strata, not far 

 above the "Cinder" in the middle Purbecks, where the brackish- 

 water series commences in a bed of shaly blue and brown marl, in 

 which I found the claw of an Astacus. In all probability, that 

 portion of the series from Nos. 55 to 70 (middle Purbecks), which 

 immediately reposes on the " Cinder," most nearly coiTesponds 

 with the Section at TefFont from Nos. 10 to 15. At Dallards there 

 are grits and shaly stone associated with the Insect limestone, con- 

 taining Ostrea, Cyclas, Cypi'is, and numerous scales, teeth, and 

 coprolites of Fish and Saurians. The first appearance of Archceo- 

 niscus is in the basement-beds of the lower Purbecks ; occurring in 

 the Cap at Chicks-grove, in the Yale of Wardour, where I pro- 

 cured some of very large size, associated with Ophiojjsis breviceps, 

 Egerton (Survey Mem. Decade 6. pi. 6), and a few elytra. At 

 Ridgway, near Weymouth, the same stratum, undistinguishable from 

 the Cap in Wilts, contains numerous fragments of ArchcBoniscus 

 and Fish ; but the former has never yet been detected there entire. 

 This crustacean appears to be limited to the " Cap ;" here at least it 

 has not been observed higher up in the Section. It occurs again, 

 abundantly and in clusters, towards the lower division of the middle 

 Purbecks, accompanied by a few elytra, in Durdlestone Bay (Nos. 125 

 & 127, Mr. Austen's List), and again in No. 58 higher up ; in 

 both cases, in bands of blue shale and marl, more or less indurated, 

 both of which were deposited in brackish water. The Archceonisci 

 vary in size, but the prevailing species appears to be the A. Brodiei 

 (M. Edwards), though it is probable that another species will ulti- 

 mately be determined. 



With respect to the general character of the Insect remains in the 

 lower Purbecks in Dorsetshire, it appears, from Mr. Westwood's 

 investigations*, that they agree closely with those which mark the 



* Those who are aware of the imperfect and fragmentan- state in which most 

 of the Insect remains occur in various formations in this country will understand 

 the ditficulty of the task which Mr. West wood has uudeiiaken in elucidating their 

 true characters, and will duly appreciate the result of his lahours. The beauty 

 and accuracy of the plates require no comment. — [-Vug. 14, 1854. — P. B. B.] 



