NO. 8 SARDINIAN CAMBRIAN GENUS OLENOPSIS 24I 



Geographic distribution. — The type species, Olenopsis zoppii, 

 occurs on the Island of Sardinia at Canal Grande and vicinity. In 

 North America Olenopsis roddyi is found on the eastern side of the 

 Continent near Lancaster in the central part of Pennsylvania. On 

 the western side of the Continent Olenopsis americanus is found in 

 the northern central part of Montana, and Olenopsis ? agnesensis 

 on the line of the Continental Divide near the Canadian Pacific 

 Railway in both Alberta and British Columbia. It is quite probable 

 that if entire specimens of a number of species now represented by 

 cranidia and referred to the genus Ptychoparia were available for 

 study other species of Olenopsis would be found at approximately 

 the same stratigraphic horizon. 



Observations. — Doctor Bornemann distinguishes Olenopsis from 

 Olenus on account of its having a small, rounded tail-shield with 

 unsegmented axis ; by the particularly semicircular outline of the 

 cephalon, the conic, nearly smooth glabella, and 14 or 15 body seg- 

 ments; from Liostracus, by the difference in shape of the pygidium, 

 although the similarity of the form of the cephalon is very great. 



Among American genera of the family Olenidse a number of 

 species of the genus Ptychoparia have a cephalon more or less closely 

 resembling that of Olenopsis, but the marked variation in the thoracic 

 segments and pygidium serves to clearly separate them. 



Doctor Bornemann has given a very detailed description of Olen- 

 opsis and the Sardinian species referred to it, also numerous illustra- 

 tions. In consideration, however, of the fact that his work is not 

 readily accessible to many students, I am reproducing photographs 

 of a number of specimens of Olenopsis zoppii, collected at the type 

 locality, that are now in the collections of the United States National 

 Museum. These will enable the student to make direct comparisons 

 between Sardinian and American species. 



I am in doubt about referring Olenopsis ? agnesensis to Olenopsis 

 on account of the character of the pygidium. In Olenopsis zoppii 

 and Olenopsis roddyi the pygidium is elongate and slightly marked 

 by transverse furrows on the axis, whereas in Olenopsis ? agnesensis 

 the axis of the pygidium is transverse and very distinctly divided 

 into segments by transverse furrows. The entire assemblage of 

 characters in the cephalon and thorax in Olenopsis ? agnesensis is 

 such, however, that it is included in the genus pending a study of 

 a considerable group of species that have in each characters of 

 Olenus, Ptychoparia, Liostracus and Olenopsis. 



