98 FORTT-FOURTH REPORT ON TSE t^TAtE MuSEUM. 



2. Species with confluent glabellar lobes, oblique thoracic pleurae and 

 spineless pygidium. 



(e) Selenopeltis, Corda. Type, 8. Buchi, Barrande. 

 Synonym, Polyeres, Kouault. 



To these it is necessary to add another it> include an extravagant 

 form known only from its pygidium, but whose relations are nearest 

 o the genus Ceratocephala: 



(f) Ancyropyge, sub-gen. nov. Type, Acidaspis Eomingeri, Hall. 

 (Palaeontology of New York, vol. vii, p. 71, pi. 16 B, figs. 

 15-18, 1888). 



Pygidium with a short, unsegmented, buUate axis, flanked on the 

 lateral margins by two elongate nodes. Border broad and flattened, 

 its margin bearing twelve long curved spines, four on each side and 

 four behind; the lateral members strongly recurved, the posterior 

 being straight and less divergent. ^ From the surface of the posterior 

 border arise two other spines just above and within the fourth of the 

 lateral marginal spines; these rise at an angle of nearly 45° and were 

 probably nearly of the same length as the rest. 



The character of this remarkable trilobite will be seen from the 

 accompanying copies of figures from the work above cited. 



The felicity of this grouping makes itself apparent upon attempting 

 an arrangement of the species. The more extrav1&,gant forms of 

 Ceratocephala are separated under the three divisions Selenopeltis, 

 DiCRANURUS and Ancyropyge and these are represented by but four 

 known species in all. The actual morphological value of the latter 

 is undoubtedly higher and they are better entitled to independence 

 than the remaining groups. 



The American Species of Ceratocephala 



In the palaeozoic faunas of North America the genus Ceratocephala 

 is not largely represented. 



It has been observed that the earliest species described is the G. 

 goniata, Warder, 1838, with which, it seems to us, the Acidaspis Danai, 

 Hall and A. Ida, Winchell and Marcy, are synonymous. 



In a supplementary note to Warder's paper in the American Journal 

 of Science, J. G. Anthony described the species G. ceralepta. The 

 woodcuts accompanying this description represent two inverted 

 pygidia of small size, the long marginal spines being regarded as 

 antennae. Mr. Meek subsequently identified, v^ith some doubt, this 

 species from the Hudson river group at Cincinnati, Ohio,* the original 



* Palaeontology of Ohio, Vol. I, p. 169, pi. 14, flgs. 8, 9, 1873. 



