94 BULLETIN OF THE NATURAL HISTORY SOCIETY. 



Report on Geology. 



It may be of interest to the members of this Society to know- 

 that the Cambrian rocks of St. John have yielded several brachi- 

 pods, which have thrown considex-able light on the early history 

 of this o-reat class of the mollusca ; a group of much greater 

 importance in past time than now : but of which, nevertheless, 

 several very ancient types have subsisted until the present time. 



The progress which has been made of late years in the 

 knowledge of this ancient group, has led to the suggestion of 

 several systems of classification, looking to the incorporation of 

 this new knowledge. 



One of the latest systems of classification is that proposed by 

 Prof. Chas. E. Beecher, which has been amplified and extended by 

 Chas. Schuchert, and illusti-ated by Prof. J. M. Clarke and Miss 

 Agnes Crane. In this system the position of the opening or pas- 

 sage for the byssus or thread, by which the shell was anchored, 

 is taken as of primary importance in classification.* Thus 

 there are the (1) Atremata, in which there is no passage through 

 the shell for the byssus, or merely a groove in the edge of one of 

 the valves. (2) The Neotremata in which the shell may have 

 a perforation at various distances, from the back of the valve 

 along the central line. (.3) The Protremata, in which there 

 is a slit at the back, more or less completely closed by a 

 plate. (4) The Teleotremata, which belong to a period later 

 than the Cambriam, and in which the " arms " within the shell 

 have a calcareous supporc. 



Some primitive and therefore, to the naturalist, highly inter- 

 teresting examples of genera of the first three orders are found 

 in the Cambrian rocks at St. John, among which may be named 

 for the first order, Botsfordia jyulchra (Matt.), the young of which 

 have the form of the most primitive type of Brachiopod known ; 

 for the second order Trematoholus insignis (Matt.), (figured 

 below), which unites the general characteristics of the first order 

 with the perforated valve of the second and the articulating 

 hinge of the third ; for the third order, Protorthis Billiiigsi 

 (Hartt), remarkable for the broad low opening in the valves, and 

 its resemblance to the genus Orthis of later Cambrian time. 



* The value of this character in the classiflcation of the Brachiopoda was urged 

 a good many years ago by Prof. Jas. Hall of Albany. 



