Geology and Mineralogy. 329 



13. Optical Pyrometry. — A paper by C. W. Waidner and 

 G. K. Burgess in the second number of the Bulletin of the 

 Bureau of Standards (see also p. 91, Jan., 1905) gives a thorough 

 discussion of the subject of optical photometry, both as regards 

 theory and methods. The experimental comparison of the vari- 

 ous types of optical pyrometers is particularly thorough and valu- 

 able. The authors conclude, on the basis of their experiments, 

 that the several laws of radiation are in quite satisfactory agree- 

 ment at the highest attainable temperatures and thus serve to 

 define the same scale of temperatures. For example, they state 

 that " it would seem that the radiation laws are still in agree- 

 ment at the temperature of the arc. Our measurements have 

 given as the black body temperature of the hottest part of the 

 positive crater 3690°, 3680°, and 3720° absolute, as determined 

 with the Holborn-Kurlbaum, Wanner, and Le Chatelier pyrom- 

 eters, based on the extrapolation of Wien's law. Fery gets for 

 this temperature 3760° by a method based on Stefan's law." 



II. Geology and Mineralogy. 



1. Cambrian Brachiopoda with Descriptions of New Genera 

 and Species ; by Charles D. Walcott. Proc IT. S. National 

 Museum, xxviii, 1905, pp. 227-337. — This is the sixth paper of the 

 preliminary studies for the monograph on the Cambrian Brachi- 

 opoda, to be published by the IT. S. Geological Survey. In it are 

 described 106 new species, 50 old species, 8 old genera, and the 

 following new genera or subgenera : Otusia (type Orthis sancl- 

 bergi Winch ell), Nisusia (type Orthis festinata Billings), James- 

 ella (type Orthis perpasta Pompeckj), Eostrophomena (type E. 

 elegantula new), Orusia (type Orthis lenticularis Wahlenberg), 

 Finkelnburgia (type F. finkelnburgi new), Loperia (type L. 

 doiigaldensis new), Swantonia (type Camarella antiquata Bil- 

 lings), Bustella (type B. edsoni new), Gurticia (type G. elegantula 

 new), Quebecia (type Obolella circe Billings), and Schuchertina 

 (type S. cambria new). 



As the generic name Iphidea Billings, 1872, was preoccupied 

 by Boyle, 1865, Dr. Walcott here changes the name to Iphidella. 

 However, as two other generic names have been proposed for 

 species referred by Walcott to Iphidella we are obliged under 

 the rules of nomenclature to replace his by one of these names. 

 The earliest one is Meek's 3Iicromitra (type Iphidea (?) sculpti- 

 lis), or Beecher's Paterina (type Obolus labradorica). As I. 

 sculptilis has an ornamental surface, it may be well to retain 

 Micromitra in a subgeneric sense, in which case we are forced to 

 adopt Paterina for the unadorned forms to replace the pre- 

 occupied name Iphidea Billings. 



From the six papers thus far issued, it is evident that Dr. Wal- 

 cott's monograph is not only to be a monumental volume, but 

 that students of brachiopods will have a firm foundation on which 



Am. Jour. Sci. — Fourth Series, Yol. XIX, No. 112. — April, 1905. 

 22 



