78 
Kirtley F. Mather 
Gastrioceras is represented by three species none of which is, 
known to occur elsewhere though one, G. hranneri, was described 
several years ago by Smith. The genus appears to be especially 
characteristic of the mid-Carboniferous times. 
Trilobites are represented by numerous pygidia which might 
as well belong to species of Phillipsia as of Griffithides, and by 
two types of glabella, both belonging to the latter genus. Affini- 
ties with other trilobite species are not conspicuous. 
Summarizing the foregoing paragraphs, it appears that the 
transitional aspect which characterizes the Morrow fauna is dis- 
played in greater or less degree by each of the classes of inver- 
tebrates which compose it. The following list includes the most 
typical of the forms representing the residual Mississippian 
element : 
Residual Mississippian Element of the Morroiv Fauna 
Amplexus corrugatus 
Pentremites angustus 
Pentremites rusticus 
Cromyocrinus grandis 
Stenopora tuberculata 
Anisotrypa sp. 
Fenestella serratula 
Archimedes juvenis 
Rhombopora attenuata 
Rhombopora tabulata 
Glyptopora crassistoma 
Dielasma arkansanum 
Brachythyris laticosta 
Spiriferina transversa 
Eumetria vera 
Sphenotus halensis 
Aviculopecten talboti? 
Lepetopsis chesterensis? 
Bellerophon cf. sublaevis 
Straparollus cf. spergenensis 
In contrast with the residual element the forms listed below 
may be cited as representatives of the proemial Pennsylvanian 
facies. Those not included in the two lists are of indefinite 
affinities or of little value, in the present state of knowledge, 
as indicators of time relations. 
Proemial Pennsylvanian Element of the Morrow Fauna 
Zaphrentis gibsoni 
Lophophyllum profundum 
Campophyllum torquium 
Michelinea eugeneae 
Chaetetes milleporaceous 
Eupachycrinus cf. magister 
Delocrinus dubius 
Delocrinus pentanodus 
Delocrinus sp. 
Polypora elliptica 
Squamularia perplexa 
Squamularia transversa 
Spiriferina campestris 
Hustedia brentwoodensis 
Hustedia miseri 
Edmondia subtruncata 
Nucula parva 
Leda bellistriata? 
Parallelodon sangamonensis 
Myalina cuneiformis? 
