374 Reviews — Barrande's Silurian of Bohemia. 



"With regard to duration Dr. Perner divides the genera into two 

 series, viz. : — 



A. Those which are confined to only one 'bande', of which there 

 are 95. 



B. Those which exist in more than two contiguous ' bandes ', whose 

 number is only 7. 



Ten genera are more especially remarkable for their longevity, viz., 

 Carinariopsis, Clisospira, Ci/rtolites, Eury%one, Hercynella, Palaacmcea, 

 Loxonema, Platyostoma, Turbonitella, and Ectomaria. The four genera 

 Bemlexia, Callocomis, Mourlonia, and Troclwnema are peculiar for 

 their manner of reappearing after long periods of absence. This is 

 an instructive instance of the imperfection of the record. 



E-el, and e2, are especially closely connected, having nineteen 

 genera in common ; but there is an appreciable break between e 1 

 and D, for they have only one genus in common. There is also 

 a decided break between F-f 1 and f 2, which is both palseontological 

 and petrographical ; only five genera are common to both divisions. 

 F-f 1 is very poor in fossils, while f 2 is remarkably rich and has 

 thirty-four genera in common with E-e2. Gr-g 1 has only seven 

 genera in common with F-f 2. 



The nature of the matrix is in a great measure accountable for the 

 abundance of fossils in E-e 2 and F-f 2, as the rock is for the most 

 part calcareous. 



The greater number of species also occur in a single 'bande', there 

 being but thirty-nine species common to two contiguous ' bandes ' 

 (E-el, and e 2), and only two species appearing in both E-e 2 and 

 F-f 2. The reappearance of species in succeeding 'bandes' only 

 attains about 6 per cent, of the total number of species, and most 

 of these are confined to E-e 1, e 2, and F-f 1 (Sil.). 



Thus, owing to their less frequent recurrence, Dr. Perner regards 

 the Bohemian Gasteropoda as of even greater service in the 

 determination of the age of horizons than the Trilobites, Cephalopods, 

 and Brachiopods, 



A chapter is devoted to genetic relationships, but Dr. Perner does 

 not consider our knowledge of genera, especially of those from foreign 

 localities, sufficient for accurate deductions. 



A list of twenty-nine species common to Bohemia and other 

 countries is given, but this likewise cannot be looked upon as 

 absolutely correct on account of the imperfection of the figures and 

 descriptions hitherto published in most countries. Only four — two 

 Silurian and two Devonian — are identified with British species, and 

 it is very doubtful if the two former are conspecific. 



Dr. Perner also gives a table of species from other countries, greatly 

 resembling, though not identical with, Bohemian ones. 



The immense importance of the work seems to justify the details 

 entered into here, which, after all, give but a mere outline, the limits 

 of space rendering it impossible to give more. The value of such 

 a treatise to students of Palaeozoic palaeontology is apparent, and they 

 must all feel deeply indebted to Dr. Perner for this painstaking and 

 laborious contribution to science. 



Jane Longstaff (Donald). 



