84 



features which the Quebec specimen shows distinctly. The main 

 difference is of size. The plates in the Canadian example of Nidulites, 

 are considerably smaller than those in the type of Salter's species from 

 Europe* : there being ten plates in the space of one centimetre in the 

 former and six plates in the same space in the latter. This species has 

 not heretofore been recorded in Canada, and forms an interesting 

 addition to our fauna. 



Note. The occurrence of this species along with many of its 

 associates also points to the close relation which probably exists between 

 the rock formations of the Girvan succession in Scotland, and those of 

 the fossilferous ' Quebec group : in Canada, a correlation which had 

 already been made apparent to the writer on account of the similarity 

 of the faunas. 



CCELEXTERATA. 



2. Streptelasma cortiiculum, Hall. A small and rather obscure 

 turbinate coral occurs in the collection. From its characters and 

 affinities it appears to be closely related to the ordinary Trenton form 

 described by Hall from the New York series. The Quebec specimen 

 is here referred to in this species with some uncertainty. 



3. Dip/ograptus, cf D. rugosus, Lapw. Among the specimens 

 collected on Mountain Hill only one graptolite occurs, and that appears 

 to be a diplograptid, allied to Prof. Lapworth's D. rugosus. It is not 

 well preserved, and the hydrothecae are somewhat irregular and recall 

 D. amplexicaulis of the Trenton. 



Bryozoa. 



4. Pachydictya acuta ? Hall. A number of broken and more or 

 less imperfectly preserved stipes of this species occur on the weathered 

 surfaces of the limestone. Note. Besides the above species of Polyzoa 

 (Bryozoa) doubtfully referred to P. acuta, Hall, there are several 

 fragments of branching Bryozoa which require to be examined micros- 

 copically in thin sections before they can be determined with any degree 

 of accuracy. From a mere superficial examination of the zocecial aper- 



*See Nicholson and Etheridge, lr., "A Monograph of the Silurian fossils of the 

 Girvan District in Ayrshire, I., p. 18, 1874." 



