Report of tee State Geologist. 



373 



Plate XXXVI.— Tarrilepas cancellatus. Fig. 2. 



Turrilepas devonicus. Fig. 3. 

 Plate XXXVI.— Tarrilepas nitidulus. Fig. 4. 



Tarrilepas squama. Figs. 5, G, 7, 8. 



Tarrilepas tener. Figs. 9-10-11-12-13, 14. 



Turrilepas foliatus. Fig. 15. 



Strobilepis spinigera. Figs. 20-21-22. 



Palaeocreusia Devonica. Figs. 24-25-2G. 



Total number type specimens 348 



Total number casts of type specimens 34 



382 



PALAEONTOLOGY OF NEW YOEK— Volume VIII. 

 Historical Statement. 



During the preliminary studies of the Brachiopoda, now illus- 

 trated in volumes III and IV of the Paleontology of New York 

 (the latter in 1867), the author became aware of the necessity of a 

 revision of the genera of this class of fossils as then recognized 

 and described. In the course of this work and in the final prepa- 

 ration of these volumes, he had already proposed the establishment 

 of seventeen new genera, which, though opposed and criticised 

 as being unnecessary or not well founded, have since been 

 adopted in the science. More than this, the recent workers 

 in the same direction of investigation, have seen the necessity of 

 establishing other new genera. Mr. Davidson, the most learned 

 in the Brachiopoda, as well as the most strenuously conservative 

 in his views of generic subdivision, after protesting against the 

 proposed subdivisions, finally yielded to the evidences offered by 

 the study of the interior appendages, hinge structures and the 

 muscular and vascular impressions upon the interior of these 

 fossil shells, and since that period has himself added a consider- 

 able number of new genera. 



Other workers in this field have departed still more widely 

 from the originally accepted genera of twenty-five years ago ; and 

 while new generic types are being discovered, some of the older 

 genera, recognized as established groups, are found to be com- 

 posed of very heterogeneous material, which requires subdivision. 



But while congratulating ourselves that such progress has been 

 achieved during recent years we should not forget to recognize 

 the results published by Pander more than forty years ago. For 

 a long time the generic subdivisions recognized and published by 



