102 The Ottawa Naturalist. [Nov. 



The third group contains but a single species, the Agnostus? 

 nobilis of Ford. This form differs from all other known 

 Eodiscidae in lacking the dorsal furrows on both cephalon and 

 pvgidium, and has thus the appearance of an Agnostus of the 

 laevigati group. A nearly complete specimen of this species 

 was recently found at the Lower Cambrian exposure on Pearl 

 Street, North Weymouth, Mass., by Mr. T. H. Clark, and the 

 specimen is now in the Museum of Comparative Zoology at 

 Harvard University. The species has previously been known 

 only by the single specimen which served Ford as a type. That 

 specimen was poorly preserved, and has been lost since its 

 description, so that the rediscover}- of the species is of consider- 

 able interest, and it adds a new species to the rather scanty 

 fauna of the Paleozoic of Massachusetts. Mr. Clark's specimen 

 shows nearly all the dorsal shield, though the head is displaced 

 from the body, and a part of one side of the thorax is missing. 

 The presence of three segments in the thorax shows conclusively 

 that this species belongs to the Eodiscidae and not to the 

 Agnostidae. Both cephalon and pygidium are nearly circular, 

 both have a narrow flattened border, and this border on the 

 cephalon shows the row of small tubercles so often seen in this 

 family. Neither cephalon nor pygidium shows the dorsal furrows 

 or other markings, though by holding the specimen at a certain 

 angle it is possible to make out the outline of a wide median lobe 

 on the pygidium. The specimen is 7.5 mm. long. Since the type 

 of Agnostus? nobilis is lost, this specimen may now take its place, 

 and it becomes the type of the third group of the Eodiscidae, 

 to which the name Weymouthia may be applied. 

 Family Eodiscidae, Raymond. 



Hypoparia of small size, cephalon and pygidium sub-equal, 

 free cheeks absent from the dorsal side, thorax of three segments. 

 Pygidium annulated or smooth. Lower and Middle Cambrian. 

 Northern Europe and Eastern North America. 

 Genus Eodiscus, Matthew. 



Eodiscidae with short glabella, and long or blunt neck spine, 

 pygidium with a long ringed axial lobe and smooth side lobes. 

 Type, Eodiscus schucherti, Matthew. Lower and Middle Cambrian. 

 Europe and North America. 



Genus Goniodiscus, nov. 



Eodiscidae with long glabella, usually blunt neck spine, and 

 pygidium with rings on the axial lobe and ribs on the pleural 

 lobes. Type, Microdiscus lobatus, Hall. Lower and Middle 

 Cambrian. England and Eastern North America. 



Genus Weymouthia, nov. 



Eodiscidae without dorsal furrows on cephalon or pygidium, 



