262 bulletin: museum of comparative zoology. 



been interchanged, for the specimen having the wide border in front 

 is labeled A. rovvingcri, while the description states that A. iviscon- 

 sen^is has the wide border. With the exception of this single char- 

 acter, the width of the flat border in front of the glabella, the two types 

 are in perfect agreement. Raymond and Narraway, without seeing 

 the types, hazarded the opinion that Walcott's two names represented 

 only one species, and cited the fact that in their collections, the border 

 was wider in young specimens than in older ones. Jt is true that the 

 type of AsapJms ronmigcri is larger than that of A. wisconscnsls, but 

 the other specimens in the collection fail to bear out our suggestion. 

 Beside the type, there is only one other specimen which will answer 

 the definition of Asaphus romingeri, and that is somewhat smaller 

 than the type of A. unsconsensi^, while there are several specimens of 

 A. wisconscnsis which are larger than the type of A. romingeri. This 

 difference in the width of the border certainly does exist among adult 

 specimens, and while it does not seem to be of specific value, it is a 

 character which may later prove of use. 



Clarke's types of Ptychopyge ulrichi were two pygidia from Cannon's 

 Falls, Minnesota, and they agree with pygidia from Platteville, Wis- 

 consin, and Newport, New York, except that a complete pygidium of 

 the same size as Clarke's large fragment shows a much shorter form 

 than is indicated by his outline restoration. 



The collection of the M. C. Z. contains, beside the specimens in the 

 Walcott collection, which are all from Russia (Newport), New York, 

 a number of cranidia and pygidia, and one nearly complete specimen, 

 from Platteville, Wisconsin. The specimens in the Walcott collection 

 were presumably all used in describing Asaphus romingeri and A. wis- 

 consensis, although there are pygidia present, a fact not mentioned in 

 the original descriptions. 



The nearly entire specimen is flattened, and is somewhat imperfect 

 in several particulars, but shows fairly accurately the general propor- 

 tions of the animal. The cephalon is large, occupying .43 of the length 

 of the animal, while the thorax occupies .27, and the pygidium .30. 

 The axial lobe is narrow, .32 of the total width, and the cephalon and 

 pygidium are both nearly semicircular, the length of the cephalon 

 being .55 of the width, and the length of the pygidium .53 of the width. 

 These general proportions accord very well with a specimen of Isotelus 

 gigas 3.5 mm. long, except that the thorax being complete in the 

 Basilicus, it makes the whole animal longer. 



Separated cranidia from St. Joseph Island, Lake Huron, (in collec- 

 tion of the Geological survey of Canada), from Ottawa, Ontario, 



