Discoveries in the St. John Group. 139 



The oldest fauna is found in the band b. It is littoral, and its 

 deep-sea equivalent is not known, but its crustaceans differ from 

 those of the next band. The connecting link between the fauna 

 of this band and that of the band c above it, is found chiefly in 

 the brachiopods and pteropods. In the fauna of b are two new 

 types of bivalve crustaceans. The solitary trilobite known, 

 Agraulos (?), is notable for tbe ureat development of the 

 axial lobe of the cephalic shield and thorax, and of the close 

 approximation of the eyes to the glabella. In this feature it re- 

 sembles Conocoryplie lyellii of the Welsh Cambrian strata. Two 

 species of the pteropods display the remarkable feature, in this 

 class, of a camerated shell, and were apparently adapted to resist 

 the accidents of life on a sandy sea-shore. As for the brachiopods, 

 we find among them only the most primitive types — Linnarssonia, 

 Lingulella, Acrothele and Acrotreta. 



On passing to the beds of band c a host of new forms present 

 themselves, among which are two types of sponges,Protospongia (?) 

 and an undescribed genus. The cystidian, Eocystites, also appears 

 at this horizon. To the genera of brachiopods referred to as found 

 in band b are now added three species of the genus Orthis, and 

 another Lingulella takes the place of that found in band b. Among 

 the gasteropods are several genera : Stenotheca, SceneUa, 

 Harttia, etc. The pteropods are well represented in hyalithoid 

 species of three different types. The bivalve crustaceans have a 

 fair representation ; those of the underlying band are not found 

 but new species appear, including those of the genera Primitia, 

 Leperditia, etc. The trilobites are represented by the most ancient, 

 genera : — Agnostus has four species, Microdiscus two, Ptychop- 

 aria five or more, Conocoryplie three, an ancient type of Ctenoce- 

 phalus one, and Paradoxides four ; all four of this last genus have 

 continuous eyelobes. 



Passing to the beds of the new band, viz., d, a change in the 

 fauna is at once apparent, (hough a connection with the preceding 

 fauna is maintained by the presence of the undescribed sponge, 

 all of the pteropods, and two familiar forms of brachiopods — Lin- 

 narssonia and Acrothele; there are also varieties of the Agnosti, 

 the Ptychopariae, and of Protospongia (?) of band c. On the 

 other hand, quite a number of new species appear at this horizon, 

 among which may be named a Dendrograpsus (?), another Lin- 



