CLASSIFICATION. 13 



serpentinus is by Haug placed in the genus Hildoceras. In the Inferior Oolite 

 there are some species which very closely approach the type of this genus, but 

 may have to be separated. The only other genus of Hyatt's that we need remark 

 upon is that of Hammatoceras (see Hyatt, page 88), mentioned again on page 98 

 and spelt Ammatoceras. Under this genus, the type of which is Ham. insigne, 

 have been placed by some authors a number of Inferior Oolite species such 

 as Sowerbyi, adicrum, patella, &c. These species have been generally placed 

 in the genus Harpoceras, which was created by Waagen to include the Falciferi 

 and Insignes. Dr. Wright, too, in his Lias Monograph has adhered to the 

 plan of keeping the Insignes in the genus Harpoceras. Previously, however, 

 Neumayr 1 in a very interesting paper, had expressed his opinion that it was 

 advisable to keep Hammatoceras for the group of Am. insignis, and this plan has 

 been followed by the majority of Continental authors. Bayle, however, in the 

 same year in his ' Explication de la Carte geologique de la France,' proposed the 

 genus Waagenia for a species allied to Am. Sowerbyi. The name Waagenia, how- 

 ever, having just previously been used by Neumayr, was changed to Sonninia 

 (see ' Bullet. Societe geol. France,' vol. vii, series 3, page 92, 1878-79). 



In 1869 Waagen proposed the name Harpoceras as a generic name for all those 

 Ammonites with falciform sculpture and distinct keel, and cited as his examples 

 of this genus, Harpoceras Actaeon, Masseanum, and arietiforme, which belong to 

 the Falciferi of the Lias ; and he proceeds to say that next come the Insignes, the 

 Falciferi of the Brown Jura with keeled body chamber, Harp, opalinum, Edouardi- 

 a nu in, hecticum, Henrici, canaliculatum, trimarginatum, and lastly Harp. Zio? Hyatt 

 had, however, a year or two previously more minutely divided a large portion of Am- 

 monites, 3 and had dealt with part of these very fossils which Waagen here mentions. 

 He had divided what Waagen wished to called Harpoceras, as far as the Lias is 

 concerned, into four families — Phymatoidse, Cycloceratidee, Discoceratidse, and 

 Hildoceratidse; and into eight genera — Phymatoceras, Hammatoceras, Tropidoceras, 

 Ophioceras, Pelecoceras, Flildoceras, Grrammoceras, Leioceras. These divisions 

 were, however, thought too fine, and we consequently find that Waagen's genus 

 Harpoceras was more generally used. Tate and Blake 4 use it throughout their 

 work, and Dr. Wright throughout the whole of his Monograph in the entire form 

 in which Waagen proposed it. Now, however, that smaller divisions are found 



1 Neumayr, " Ueber unvermittelt auftretende Cephalopodentypen," &c, ' Jahrbuch der K. k. 

 geologischen Reichsanstalt,' Band xxviii, 1878, pp. 37-80 (see footnote, p. 67). I would also call 

 attention to another important paper of Neumayr' s in ' Zeitschrift der deutschen geologischen 

 Gesellschaft,' Band xxvii, 1875, where the generic grouping and classification of Ammonites is most 

 thoroughly worked out. 



2 Waagen. 'Die Formenreihe des Ammonites subradiatus,' 1 p. 250 (72). 



3 Hyatt, ' Bulletin of the Museum of Comparative Zoology of Harvard College,' 1867, pp. 71 — 102. 



4 ' The Yorkshire Lias,' 1876. 



