Reviews — Bollettino della Societd Sismologica. 379 



into families and genera, or in founding wholly artificial groups. 

 Consequently the systematist is compelled to trust to zoarial 

 characters. When he finds that a change in environment appears to 

 bring about a change in zoarial habit in a species, and that types of 

 zoarial growth characteristic of different "genera" may occur in the 

 same specimen, and further, that transitional forms link together the 

 types of zoarial growth assumed to be of generic or family importance, 

 then it is that be feels the need of caution in applying such terms as 

 family and genus to groups of forms classified according to zoarial 

 characters. As a philosophical naturalist, Dr. Gregory is inclined to 

 group at least the first section of the Tubulata under one genus. 

 As a working palaeontologist, he retains the well-known generic 

 names, but with the understanding that such names are merely 

 labels attached to certain groups, the members of which resemble 

 each other more than the members of neighbouring groups. In 

 place of the word " genus " Dr. Gregory suggests " circulus." a 

 term applied to the groups of listeners which congregated round 

 orators in the Forum. 



Minor characters of the zocecial tubes are made use of to dis- 

 tinguish species. Dr. Gregory has framed a very useful "variational 

 formula," whereby " the range of variation within the limits of a 

 certain specific group may be conveniently shown." The elements 

 taken into account are the peristome or distal end of the zooecia, 

 the shape, the length, and the amount of aggregation of the zooecia, 

 four degrees (0, 1, 2, 3) of variation being calculated. By means 

 of this formula, it is easy to accurately tabulate and compare the 

 slight variations that may occur, let us suppose by way of example, 

 in specimens of the same species occurring in consecutive strata 

 or epochs. 



We regret to have to point out that a short corrigenda list is 

 necessary. Tlie text is liberally illustrated by numerous woodcuts, 

 and by eleven plates, the artistic finish of which is excellent. 



Laborious research, scientific method, and artistic skill have con- 

 tributed to form a volume which maintains the honourable traditions 

 of the British Museum ; and it is to be hoped that Dr. Gregory will 

 complete the work he has so well begun. 



II. — Bollettino della Socteta Sismologica, Vol. I, 1895. 

 pp. 168 + 230. 



DE ROSSI'S valuable Bullettino del Vulcanismo Italiano was begun 

 in 1874, and ceased to exist in 1889 or 1890 after a few parts 

 of the seventeenth volume had been published. Its place is now 

 worthily supplied by the Bollettino of the Italian Seismological 

 Society, founded under the direction of Prof. Tacchini in the spring 

 of last year. Though nominally a society, it does not appear that 

 any meetings have been held ; indeed, the members are so widely 

 scattered, so few are collected in any one place, even in Rome, that 

 regular meetings would be hardly possible, and the exertions of the 

 members are wisely confined to the publication of their journal. 

 The first part of the volume contains 27 short papers. The second 



