174 Reviews — Beecher and Clarke — Silurian Brachiopoda. 



was made in the Niagara group at Waldron, Indiana, for the New 

 York State Museum (Albany, N.Y.) ; the specimens were separated 

 from the shales by washing and passing the material through sieves 

 of different degrees of fineness, and by this means a vast number 

 (about fifty thousand) of partly developed shells were obtained, most 

 of which were less than five millimetres, and many not more than 

 one millimetre in length. After rejecting imperfect and badly 

 preserved specimens, more than fifteen thousand immature individuals 

 still remained for examination. Besides the embryonic Brachiopoda, 

 immature forms of Gasteropods and Crinoids were also found, but 

 the material was not sufficiently promising to repay investigation. 

 The number of species and varieties of Brachiopoda obtained from 

 the Waldron Shales was forty-two, ascribed to twenty-four genera. 

 Twenty-six of these species furnished data for the observation of 

 developmental changes ; of the rest no young shells were obtained. 

 The genera represented were Crania, Lingida, Pholidops, Orthis, 

 Streptorhynchus, Strophomena, Strojyhodonta, Stroplionella, Leptama, 

 Streptis, Chonetes, Eichwaldia, Pentamerus, Anastrophia, Rhynchonella, 

 Rhynclwtreta, Atrypa, Zygospira, Ccelospira, Retzia, Nucleospira, 

 Meristella, Whitfieldia, Spirifer. Of these the following species 

 appear to have yielded the best results : — Streptorhynchus subplanum, 

 Conrad ; Strophomena rhomboidalis, Wilckens ; Stroplionella striata, 

 Hall; Meristella rectirostra, Hall; Spirifer crispus, Hisinger; S. crispms, 

 var. simplex, Hall; S. radiatus, Sowerby ; and S. bicostatus, var. 

 petilus, Hall. 



The illustrations (plates i. — vii.) consist of enlargements of the 

 embryonic shells, usually to the size of the adult, accompanied by 

 figures of the full-grown shells, or, if the latter were too minute to 

 show details of structure satisfactorily, these also were enlarged to 

 the requisite size. Figures of special structures, such as the hinge, 

 are also added. Plate viii. represents a series of specimens ranging 

 from the very young to the adult shell ; four species are figured, 

 viz. Orthis elegantida (27 examples), StreptorJiynchus subplanum (13 

 ex.), Bhynchotreta cuneata (20 ex.), Retzia evax (27 ex.). These 

 show the character and completeness of the material serving as the 

 basis of the work. The descriptions of the species are thus arranged: 

 first, the developmental characters are taken up, and secondly, the 

 specific characters of the mature form, and then those of the "in- 

 cipient " form, and finally the developmental phases of the latter 

 are described, as to their general shape, beaks, foramen, plications, 

 etc. A useful summary of these changes is furnished at the end of 

 the book, under the heading, Size and Contour ; Valves ; Beaks ; 

 Cardinal Area; Internal Apparatus; Surface Ornaments; Varieties 

 and Abnormalities ; Senility. Of these the Cardinal Area afforded 

 by far the most important phylogenetic results, and accordingly the 

 authors have devoted several pages to a discussion of the various 

 phases it presents in different species. After describing the develop- 

 ment of the ventral cardinal area, the authors observe that their 

 results, " though derived from the species of a single fauna, must 

 not be given too limited an application, for they involve nearly 



