SUPPLEMENT.— POLYMORPHIDJE. clxix 



II. REVISION OF, AND ADDITIONS TO, TDK POLYMORPHIDJE. 

 Family— POLYMORPHID^E, Haug. 



1891. PoLYMoitPinn.K, This Monogr., }>p. 231, et seq. 



The principal character which distinguishes the members of this family from 

 the Hildoceratidae is the suture line, with its inner lobes pointing obliquely across 

 the whorl towards the periphery. There are cases, however, in which this 

 character fails — for example, in degenerate species of Dumortieria, and in the 

 genera, Gatulloceras and Tmetoceras. In style of ribbing most of the members of 

 this family may be distinguished from the Hildoceratidae — the ribs run straight, or 

 nearly straight, across the whorl, having little of that lateral bend which is often 

 so conspicuous in the Hildoceratidae, and little of the ventral projection (rostration) 

 which is sometimes so marked in that family. 



The manner of phyletic development, however, is the chief point to be noticed. 

 Whereas the Hildoceratidae attain to a marked tuberculate stage with a well- 

 developed carina — e.g. Lillia, Haugia, Denchmannia, Ohartronia, Kiliania, etc. — and 

 then show the stages of decline through a costate to a smooth stage, the Polymor- 

 phidae only attain to a parvituberculate stage when the carina has not been de- 

 veloped, or is only feeble; examples, Tmetoceras, no carina, sulcate periphery; 

 Uptonia, costate periphery; Acanthopleuroceras {Gycloceras), feeble carina; while in 

 Dumortieria and Gatulloceras there is no evidence of a tuberculate stage having been 

 attained : it seems as if the anagenetic costate stage passed direct into the cata- 

 genetic, and the carina is a feature developed in the catagenetic costate stage. 

 But in the Hildoceratidae, on the evidence of ontogeny and analogy with the 

 Arietidae, the carina is developed even before the anagenetic costate stage com- 

 mences. 



When the members of this family were described in the body of the work, only 

 a few localities were known to yield the principal genera — Dumortieria and Gatul- 

 loceras; and the examples were mostly poor. Much addition has been made 

 since. Mr. Charles Upton found in Penn Wood, near Stroud, a rich fauna of 

 Dumortieria. This locality, and Buckholt Wood, near Frocester, have yielded to 

 him and to myself many good specimens. Dursley also afforded me a good series 

 in nice condition — mostly from the Moorei beds. The late Mr. E. Wilson, F.G.S., 

 and Dr. Vaughan, F.G.S., have sent me various species from the neighbourhood of 

 Bath and Bristol. Mr. Blooinfield showed me two localities in the Yeovil Sands, just 

 out of Yeovil, rich in Dumortieria and Gatulloceras — mostly of a type distinct 



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