THE PALEONTOLOGY Of MINNESOTA. 



IGerasaplies ulrlchana. 



broadest; all are simple, unfurrowed, and all disappear quite abruptly at the marginal 

 border. The posterior portion of the pleurae is smooth, and the extremital area of the 

 border is slightly bent upward. The entire surface of the shield is covered with 

 anastomosing, racemose, elevated lines, which are very conspicuous on the larger 

 specimen, and clearly apparent on the smaller. This ornament is one of the generic 

 characters of the group given by Angelin: "densissime striolatus." This species is not 

 widely different, so far it is known, from Asaphus huttoni Billings,* from the Quebec 

 group of Table Head, Newfoundland, except in the length of the axis, which exceeds 

 that of the latter species. It is an excellent representative of the strongly segmented 

 type of Asaphun for which Angelin proposed the name Ptychopyye. 



Formation and locality. One of the smaller specimens is from the lower blue beds of the Trenton 

 limestone at Mineral Point, Wis. (Museum No. 8402), and the others from an equivalent or Birdseye 

 horizon at Cannon Falls, Minn. The latter are from the collection of Mr. Scofleld. 



GERASAPHES,t n.subgen. 

 GERASAPHES ULRICHANA, n. sp. 



The form for which this name is introduced, though small, and even imperfectly 

 known in certain respects, is one of no little interest in its relation to the ontogeny 

 of the asaphids. The specimens of the single known species (named in compliment 

 to its discoverer, Mr. E, 0. Ulrich) consist of two cranidia and two pygidia, lying on 

 the surface of fragments of a calcareous shale, from the horizon of the Utica slate, 

 at the mouth of the Licking river, Ohio. Of these four examples, three are on the 

 same piece of rock. The following description embodies not only the distinguishing 

 characters of the subgenus, but also those of the typical species. 



Fig. 14. Cranldium of OeratapJus ulrichana, /, 4. 



Of the two cranidia, one has a length of 4 mm., the other of 2A mm. The form 

 of this part is distinctly asaphoid. The facial sutures take their origin on the 

 posterior margin, making an acute angle with it, thence passing inward in a slightly 

 convex curve to the palpebral lobes which are situated at about one-third the length 

 of the cranidium from the posterior margin. These lobes are not large and the 

 course of the sutures in front of them is that characteristic of Isoielus, being a broad 



Paleozoic Fossils, vol. I, p. 271. BK. 237,4866. 



,*. ..lit: iim/i/ir*. :i-:i|ilms. 



