1894. SOME NEW BOOKS. 141 



from the previous work, and of Matthew's Trematobolus, which dates 

 from 1893. This part of the work is illustrated by numerous wood- 

 cuts ; at the same tim.e it will undoubtedly be necessary for those who 

 wish to gain a clear idea of the various genera, now so minutely 

 divided, to refer to the excellent plates of the larger work, and 

 better still to such specimens as they may be fortunate enough to find 

 showing the details of deltidial, muscular, and brachidial structure, 

 which specimens, we need hardly say, are rarely to be found even in 

 our best appointed museums. Owing to the great difficulty of 

 determining from ordinary specimens to which of these revised 

 genera a species should be referred, we cannot help regretting that 

 the authors have limited themselves under each genus to instancing 

 merely the type species, which of course is not necessarily a typical 

 or common species, instead of giving a list of the chief American 

 and European species that they would refer to the genus in question. 

 We may add, also, that considerable use of the larger work has 

 brought to light a defect, which is naturally intensified in this smaller 

 book, namely, a want of clearness and definiteness in pointing out the 

 characters that separate one genus from another closely allied to it. 

 It is, for instance, very difficult, in many cases, to know whether to 

 refer a species to Rafinesquina, Stropheodonta, or Oythothetes. The 

 diagnostic characters are no doubt given, but they are mixed up 

 with other characters not strictly diagnostic. This defect might 

 easily be remedied by giving a key, like that published a short time 

 ago by Mr. C. Schuchert, and we trust that some such step will be 

 taken in the second part of the present book. 



As in their previous work, the authors do not divide their genera 

 into families, a course which may be warranted by the insufficiency 

 of our knowledge, but which hardly commends itself to the text-book 

 compiler, the museum curator, or the examinee. We all admit 

 that our classifications probably do not tally with nature ; but 

 even a bad classification is better than none. The authors, however, 

 promise to discuss the question of classification at the close of the 

 work, and meanwhile we may refer to the very workable classifications 

 by Schuchert {American Geologist, xi., p. 141, and xiii., p. 102). We 

 are more inclined to quarrel with our authors for the arrangement that 

 they have in some instances adopted. They need not commit them- 

 selves to a cast-iron classification, but surely they might follow an 

 arrangement more in accordance with the facts of geological history 

 and individual development. They appear to accept the main argu- 

 ments of Beecher, but for some unexplained reason they do not admit 

 the natural conclusions. Thus, they begin with the somewhat advanced 

 Lingulidae, then proceed through the Lingulellidae and Lingulasma to 

 the Trimerellidse, from which they come back to the Obolidas, and so 

 to Patenna. Now if they accept Beecher's views on development, 

 they should also accept his conclusion that Paterina is the most primi- 

 tive form of Brachiopod known to us, and they should lead off with 

 that genus. But perhaps this will be explained in their final chapter. 

 Anyhow we know exactly what Messrs. Hall and Clarke themselves think 

 about the Trimerellidae, and we know that they derive this assemblage 

 from two distinct stocks, one typified by Lingulasma and the other by 

 Obolus, a view which may be correct, but which is at any rate incom- 

 patible with the peculiar arrangement they adopt. This, however, 

 will not render their book of less practical use to the student, who will 

 look forward with much anxiety to the second part, which we are 

 promised in the Annual Report of the State Geologist for 1893, and 

 which we may, therefore, expect to receive somewhere in 1895 '^^ 1896. 



