162 



OOLITIC OPHIURIDtE. 



shire, but differs from it by the greater proportional length of the rays and more slender 

 structure of the same ; from 0. Ramsayi, Wr., by the absence of the thorny processes 

 which project from the free angles of the lateral shields. 



Stratip'ajj Ideal Position. — This Brittle-star was first discovered by Professor H. 

 Roemer between the upper and lower Bone-bed breccias, near Plildesheim, with other 

 fossils belonging to the Avicula contorta beds. Several of these specimens were sent 

 to me for examination and description by Dr. Dames, of Berlin, and my notes on the 

 same were afterwards published, with good figures, in the ' Zeitschrift der Deutschen 

 geologischen Gesellschaft ' for 1874. 



A few months after I returned the Ophiolepis to Dr. Dames at Berlin, several 

 specimens were submitted to me which had been collected from the Avicula contorta 

 beds at Garden Cliff, on the Severn, from the dark shales above the Bone-bed. 1 had no 

 difficulty in making out the identity of this species with the one I had so recently 

 described from Hildesheim, and I brought the facts before the Cotteswold Naturalists* 

 Club at one of the regular meetings of the Society, anent the discovery of this little 

 Brittle-star in beds of the same age, and at points so far remote from each other as 

 Westbury on the Severn, and Hildesheim in Northern Germany. Very soon after this I 

 was informed that the same Ophiolepis had been collected in the black shales above the 

 Bone-bed, near Leicester. These three discoveries of this Brittle Sea-star, in beds which 

 had never previously yielded any remains of Echinoderms, made quite an epoch in the 

 history of the Avicula contorta series, inasmuch as a doubt had been entertained as to the 

 nature of the conditions under which the Avicula contorta series had been deposited : 

 many of the fossils were small dwarfed individuals which it was conjectured might have 

 lived under lacustrine conditions. The discovery of a true marine radiate in these shales 

 afforded, therefore, positive proof of the conditions under which the Bone-bed breccia 

 and its overlying shales had been formed, and recalled to my mind the important observa- 

 tion my late colleague, Professor Edward Porbes, E.R.S., had made on first seeing the 

 Avicula contorta and White Lias beds at Lyme Regis : writing to Professor Ramsay, 

 E.R.S., in 1847, he said: 



" My visit to Lyme gave me a thoroughly clear idea of the Lias, and the succession 

 of its fossils, which I much wanted, I now can picture to myself all the events of its 

 formation. At the base of it I saw the so-called White Lias, which, so far as I have seen, 

 seems to me to be essentially different from the Lias, and possibly the terminating strata 

 of the Triassic series. I broached a notion to Sir Henry De la Beche, from what I saw, 

 that the red marls were formed in a great salt inland sea (a sort of Aralo-Caspian), during 

 the hst state of which the White Lias was formed, that the bed was then either elevated 

 and converted into land, or depressed and turned into a part of the ocean, when the 

 Liassic fauna came in. This notion is not merely hypothetical ; the fossils of the White 

 Lias (very few in species) suggested the idea ; they are curiously representative of the 

 existing Caspian fauna. Such a state of things would account for the general and hitherto 



