MESOZOIC OF SOUTHWESTERN OREGON 553 



rocks. 1 The occurrence of metamorphic outliers — such as the Grous- 

 lous Mountain area of the Port Orford quadrangle — and of small 

 areas of unmetamorphosed inliers, cause but slight difficulty, which, 

 however, exists whatever criteria of discrimination be used. It may 

 be added that the two lobes which it seems logical on geological 

 grounds to detach from the Klamath Mountains, are no more related 

 to them topographically than other neighboring parts of the Coast 

 Ranges. 



NOMENCLATURE 



In approaching this field of study, the term "Myrtle formation" 

 was found applied to a number of formations which are naturally 

 separable into two distinct groups, to the upper of which alone the 

 term "Myrtle," as stratigraphically defined by its author, is appli- 

 cable. It seemed best, for the development of the subject in this 

 paper, to use a local term — "Dillard," recalling what is perhaps the 

 most typical area in the region — for the lower series as the comple- 

 ment of the existent local term, "Myrtle." 



The writer, however, is not in sympathy with the unnecessary 

 multiplying of local names. To correlate, to trace general conditions 

 and relationships, are undoubtedly among the most important aims 

 of science, and multiplicity of terms — especially synonyms — tends 

 to obscure and conceal such relationships. In particular, in the case 

 of geological formations and groups it would seem highly desirable 

 that those which the best evidence indicates as contemporaneous, 

 and which were ushered in and brought to a close by the same sets 

 of physical changes, should be designated by the same name. This 

 is especially true when they occupy the same relative position in 

 closely similar stratigraphic sequences and were formed under the 

 same general physical conditions. The rocks of the Myrtle group, 

 for example, have the same characteristic fossils, and the same strati- 

 graphic position and range, as the Shasta group of California. They 

 occupy corresponding positions in remarkably similar stratigraphic 

 sequences, and their upper and lower limits were apparently deter- 

 mined by the same great diastrophic movements. Furthermore, the 

 character of sedimentation is the same, and the distribution is such 



1 The term "Klamath Mountains" has been used in this sense throughout this 

 paper. 



