206 PROCEEDINGS OF THE PALEONTOLOGICAL SOCIETY 



STRATIGRAPHIC SIGNIFICANCE OF ORTHAULAX 

 BY C. WYTHE COOKE 



(Abstract) 



Three species of Orthaulax have been described. The genotype, 0. inorna- 

 tus Gabb, which has been supposed to be restricted to the Oligocene, was re- 

 cently rediscovered in beds of basal Miocene age (Baitoa formation) in Santo 

 Domingo at what may be the type locality. It is known also from the Tampa 

 "silex beds" (Oligocene). The stratigraphic range of O. gal)M Dall appears 

 to be very nearly the same as that of O. inornatus, but the two species have 

 never been found in the same beds. 0. gadhi comes from the Chipola marl 

 of Florida and from the Culebra formation of Panama. OrtJiaulax pugnax 

 (Heilprin) is found in the Tampa "silex beds," the lower part of the Chat- 

 tahoochee formation near Bainbridge, Georgia ; the Antigua formation, and in 

 the Culebra formation of Panama. Its known range is Middle and Upper 

 Oligocene. 



The species of Orthaulacc at Aguadilla, Porto Rico, referred to by Dr. Maury 

 under the nude name of aguadillensis, is abundant in beds supposed to be of 

 Miocene age, at Palo Copado, Azua Province, Dominican Republic, and it 

 occurs also on the Island of Saint Croix. Its range is probably Miocene and 

 Oligocene. 



A Silurian horizon, apparently new to the Boston Basin, was indicated 

 in the next paper, which was illustrated by the original specimens form- 

 ing the basis of the determination. 



PRESENCE OF UPPER SILURIAN SANDSTONE IN ESSEX COUNTY, 

 NORTHEASTERN MASSACHUSETTS 



BY A. F. FOERSTE 



{Al)stract) 



In 1893 John H. Sears, curator of geology at the Peabody Academy of 

 Science, in Salem, Massachusetts, published his Geological Map of Essex 

 County, Massachusetts, in the Bulletin of Essex Institute. On the legend 

 accompanying this map the areas colored yellow and numbered 18 are stated 

 to consist of lime slate, quartzite, and sandstone, thus indicating the presence 

 of clastic rocks. In the hope of finding fossils, the present writer, during 

 the summer of 1894, visited the area southwest of Rowley and also that ex- 

 tending from Middleton northeastward toward Topsfield. Somewhere in the 

 latter area specimens of Leperditia were found in a relatively soft quartzite 

 or sandstone, but the writer was unable to identify the species or to refer them 

 to a definite horizon. In 1918 the best specimens were submitted to Dr. R.'S. 

 Bassler, of the United States National Museum, and identified by him as 

 belonging to the Leperditia alt a group, thus suggesting the presence of strata 

 of Cayugan or upper Silurian age. 



