TRENTON CONGLOMERATE OP RYSEDORPH HILL 51 



Freeh (tab. p. 77) gives as its habitat the Knollmkalk a/3 and ad 

 which are synchronous with the GMenkiln shales (Normans kill 

 shales) and the corresponding lower middle graptolite shales 

 of Scania and of Norway. Another European form with cari- 

 na te glabella is Lonchodomas carinatus, which how- 

 ever has a more elongate cranidium, and is found in another 

 horizon (Chasmops-Kalk of Westrogothia) according to Reniele'. 

 The subdivisions of Ampyx, proposed by Forbes and Angelin, 

 have been fully discussed by Nicholson and Etheridge, 1 and 

 lately by Vogdes. 2 To restate shortly a case repeatedly eluci- 

 dated, the genus Ampyx proposed by Dalman was divided in 

 1849 by E. Forbes 8 into: 



1 Ampyx (Dalman) proper, with the head long and five seg- 

 ments of the thorax. 



2 Brachampyx Forbes, 1849, with the head short and round 

 and six segments to the thorax. 



Dr Angelin in 1854 4 proposed the subdivision of his family into 

 three genera: 



1 Lonchodomas Angelin, with a lanceolate glabella, ter- 

 minating in an elongate prismatic spine. Type L. (A m p y x) 

 ro stratus Sars. 



2 Ampyx Dalman y with an oval glabella., terminating in a 

 round spine, and six thoracic segments. Type Ampyx c o s - 

 t a t u s Broeck. 



3 Riaphiophorus Angelin, with an obiovate glabella, having 

 an abrupt apical spine, and five thoracic segments. Type R. 

 setirostris Angelin. 



It appears by a comparison of these subdivisions, that Angelin 

 retained the term Ampyx for forms with six segments, and 

 thus applied it in the sense of the originator of the term, Dal- 

 man, who described Ampyx as having six segments; while 

 Forbes proposed his term, Brachampyx, for just such six 

 segmented forms. Nicholson and Etheridge, therefore, seem 



i Monograph Sil. foss. Girvan district in Ayrshire. 1880. p. 178. ff. 



2 Am. geol. 1893. 11:99. 



3 Geol. sur. Gt. Br. Mem. Dee. 2, 1849. pt 10, p. 3. 



4 Pal. Scandin. p. 80. 



