part 1 J or the shales-with-'beef.' 55 



lower consisting of large nodules (sometimes measuring 2x3 feet) 

 surrounded by beef. The other limestones of this series are much 

 thinner and, except the Brooki Bed, less persistent. The paper- 

 shales are bounded beneath by (74 a) Little Ledge — a limestone 

 made up entirely of many layers of beef and marl-films. It is 

 very brittle, and for many yards at a time is fractured and faulted 

 for an inch or so, at intervals of about a foot, while the beds on 

 each side of it merely dip. 



The lower division of the Shales- with-Beef, approximately 40 feet 

 thick, and bounded below by (53) Table Ledge, and above by 

 (74 a) Little Ledge, consists mainly of blue conchoidal marls, with 

 occasional blue bedded marls, indurated marls, nodule-beds, friable 

 marls, and impersistent beef-seams in the upper part ; and in the 

 lower part of similar beds with frequent seams of beef and short- 

 rock. Throughout, impersistent beef-seams are often associated 

 with friable marl. The nodules (except the beds 73 a & 73 g of 

 Beef 20) are not enwrapped by beef. 



Balseontologically, the Shales-with-Beef may be divided into 

 three main divisions: namely, an upper (18 feet) corresponding to 

 the range of Microderoceras ; a middle division characterized by 

 Arietites, Sulciferites [Spath], and Amioceras, but no Agassi- 

 ceras ; and a lower division yielding Amioceras and Agassiceras. 



Only three beds of the upper division have yet yielded well- 

 preserved fossils : namely, at the top, the I? irchi-tabular, containing 

 small specimens of M. birchi associated with Xipheroceras spp., 

 Gymbites spp., and Arietites turneri; a foot below this the Birchi- 

 nodular, containing large Microderoceras birchi, Arietites plotti, 

 and allied forms l ; and a little lenticle-bed, occurring 9 feet lower, 

 containing Gymbites and Arietites, sp. nov. 



The topmost part of the middle division contains a limestone 

 full of Amioceras hartmanni, often black. Below this is the 

 Arietites-brooJci Bed, some 7 feet below which is a series of beds 

 (about 8 feet thick) wherein Amioceras is comparatively rare, but 

 Arietites and Sulciferites [Spath] are abundant. 



Sulciferites sidcifer, S. sp. cf . dumortieri, and S. sp. cf . angusti- 

 sulcatus follow from above downwards, and associated with them 

 are three new species of Arietites ; but more collecting should be 

 done before this sequence within the Sulciferites Beds can be 

 considered proved. The lowest 11 feet of the middle division 

 contain various species of Amioceras, but no Arietites or 

 Sulciferites ; and this probably marks the lowest limit of Oppel's 

 A.-obtusus Zone (see his ' Juraf ormation ' 1856, p. 52). 



The upper part of the lowest division yields Agassiceras but 

 rarely, is characterized by many species of Pararnioceras [Spath], 

 and contains abundant Amioceras. It may be correlated with 

 Oppel's ' ttiberculatus-Iiett.'' Below this are some 10 feet of marl 

 yielding several forms of Amioceras and Agassiceras, but no 



1 I have not yet found these Arietites of the A.-plotti group in place ; but 

 they occur (as noticed by Dr. Spath) on specimens associated with large 

 M. birchi, and doubtless came from this horizon. 



