ME. S. S. BUCKMAN ON THE GROUPING OF SOME [Aug. 1 898, 



Family DEEOCEEATID^.^ 

 Genus. 



Beroceras. 



Erycites. 



Hammatoceras. 



Liparoceras. 



Microceras. 



MicToderoceras. 



Flatypleuroceras. 



Family HILDOOEEATID^. 



Genus. 



Brasilia. 



Darellia. 



Grammoccras. 



GrapTioceras, 



Harpoceras. 



Haiigia. 



Hildoceras. 



Hyperlioceras. 



Lillia. 



Lioceras. 



Ludwigia. 



Folyplectus. 



Species. 

 densinodus-gron^ . 

 armatum, Bavcsi. 

 fallax, gonionotus. 

 insigne, amplectens. 

 Henleyi, capricornus. 

 hiferum. 

 Birchi. 



planicosta-gvouip. 

 latcBcosta. 

 Taylori-gvoup. 



Species. 

 acutus-grouTp, 

 boscen sis- group . 

 hradfordensis. 

 concavum-gvowp. 

 semicostata, nov. 

 striatulum, aalense. 

 ■w-scriptum, 



falciferum, Strangwaysi. 

 variabilis, jugosa. 

 hifrons, serpentinum. 

 discites, WalTceri. 

 Lilli, tirolensis. 

 opalinum. 

 MurchisoncB. 

 nann odes-gro up. 

 discoides. 



Family OPPELID^. 



Genus. 

 Cadomoceras.^ 

 lAssoceras. 

 (Ecotraustes. 

 Oppelia. 

 Strigoceras.^ 



Species. 

 cadomense. 

 oolithicum. 

 genicularis. 

 suhradiata. 

 Truellii. 



^ Tliere are three fairly distinct series in this family : — (V) Liparoceras, etc. ; 

 (2) Beroceras, etc. ; (3) Hammatoceras, etc. In Hammatoceras a strong carina is 

 developed, and the species have considerable external similarity to Sonninia. 

 The suture-line, ho\^ever, is very distinct, and attests the relationship with 

 Deroceratan forms. (' Descent of Sonninia & Hammatoceras^ Quart. Journ. 

 Geol. Soc. vol. xlv, 1889, p. 651.) 



^ This denotes an extreme gerontic form — possibly a degenerative offshoot of 

 Lissoceras. But there are homoeomorphous species, almost certainly poly- 

 genetic, and certainly heterochronous. Their similarity has caused much 

 mistaken identification ; this similarity, coupled with difference in date, has 

 made much trouble in matters of stratigraphy. 



3 With regard to Strigoceras and Strigoceratoid forms there seems to be 

 a remarkable development of closely similar forms 3 times over. The first 

 series of Strigoceratoids lived during the WitcJiellicB sp. hemera. They dis- 

 appear ; but during the niortensis hemera there lived another very similar 

 series. Then during the Truellii hemera there appeared another series, appa- 

 rently at first less developed than any of their forerunners, but ultimately 

 developing to become very similar to them. 



