NO. 3 CAMBRIAN TRILOBITES IQI 



Conoccphalitcs minor Hall, 1863, Sixteenth Ann. Rept. N. Y. State Cab. 



Nat. Hist., p. 149, pi. 8, figs. 1-4. (Describes and illustrates typical 



forms of L. chippewaensis as C. minor.) 

 Conocephalites minor Hall, 1867, Trans. Albany Inst., Vol. 5, p. 132, pi. 3, 



figs. 1-4. (Reprint of paper of 1863.) 



The type specimens of this species were from near Menomonie, 

 Dunn County, Wisconsin, where later collections show the cranidia 

 and pygidia in abundance, associated with Crepicephalus iowensis 

 and Menomonia calymenoides, which are so characteristic of the Eau 

 Claire formation. These two species are also associated with L. 

 chippewaensis at Dresbach, opposite the mouth of Black River, where 

 Shumard's specimens of Conocephalites minor came from. Shumard 

 states that Owen's species, Conocephalites chippeivaensis ( = Lon- 

 chocephalus) , is associated with his C. minor. I do not find them 

 associated at either locality of L. minor, although the range of varia- 

 tion in the glabella of L. chippewaensis sometimes brings the shorter 

 forms of the glabella close to the glabella of C. minor. 



After examining a large series of specimens from various locali- 

 ties and studying the descriptions of L. chippewaensis by Owen and 

 his illustrations, also those of Hall, I am convinced that Hall de- 

 scribed and illustrated Owen's species under the impression that he 

 was working with L. minor of Shumard. It is interesting to note 

 that he does not refer to Owen's species L. chippezvaensis, although 

 the two forms are so much alike. He speaks of a specimen sent him 

 by Shumard as being more rotund and with a proportionally shorter 

 glabella. These characters constitute the diiTerences between L. 

 minor and L. chippewaensis. It would seem that Owen's species 

 was overlooked at that time. 



In the vicinity of Eau Claire the species is very abundant and 

 ranges through the middle and upper beds of the Eau Claire forma- 

 tion ; fine specimens are also abundant at Rock Falls, Dunn County. 



Some of the cranidia have a slight longitudinal furrow on the 

 frontal limb in front of the glabella and a tendency of the*f rontal rim 

 to thicken and extend inward opposite the furrow. 



By a fortunate find at St. Croix Falls, by Dr. Samuel Weidman, 

 we now have an entire dorsal shield. This shows seven segments 

 and clearly indicates that Lonchocephalus differs materially from 

 other genera of the Olenidse in having a convex cranidium with an 

 occipital spine and a less number of thoracic segments. By using 

 the somewhat abraded dorsal shield as a base and more perfect speci- 

 mens of the cephalon and cranidium, a restoration has been made 

 as shown by figure 3a, plate 34. 



