45^ 



Dimensions : — The largest diameter of the upper surface attains 27 mm., 

 the corresponding width of the aperture being 1 1 mm, and that of the next 

 adjoining whorl 4 mm. ; the height of the shell is a little more than 10 mm. 



The single specimen from China was figured by Frecii in China vol. V. ; 

 he compared it with numerous specimens of iM. iicritoidcs from Holmstrand 

 near Christiania, Norway, and found them specifically identical. The latter 

 specimens were identified by F. Roemer with M. logani Salter^' from the 

 Ordovician of Canada. Koken pointed out the great likeness existing between 

 the European M. ncritoides and the Canadian M. logani.^'' The latter, how- 

 ever, seems to me to be provided with a narrower umbilicus. 



The original description oi J\I. lu-riioidfs given by Eichwald''' is as follows : 



" Testa magna, anfractus 2 — 3 ve latitudine subito increscentes, superne 

 plani, utroque margine externo et interno declives inque marginem inferiorum 

 obtusum excurrentes, apertura triangulari ; umbilico profondo magno." 



" La surface du test est finement striee, a stries d'accroissement transver- 

 sale tres-rapprochees." 



LoRENZ*^ described an apparently very imperfect specimen from Ho-shan 

 in Shan-tung under the name M. logmti ; he identified it with the specimens 

 of logani from Porsgrund, which may belong to M. fwritoidesJ''' So far as 

 I can judge from his figures of the Shan-tung specimen, it differs from M. 

 neritoidcs as well as from M. logani in having less rapidly enlarging whorls. 



Loc. : — No-lu-ping, Tung-hu-hsien, prov. Hu-pei ; " lower bed " (Usui 

 Coll.) 



J\I. ncritoides is known from the Lyckholm bed of Estland and the upper- 

 most Chasiiiops limestone of Norway. 



1) Salter: Ordovician Fossils from eastern Canada. Canada Geol. Surv., Can. Org. Rem., 

 Dec. I. 1859. Fhrd. Roemer: Letliaea Palaeozoica, pi. V., fig. 5. Grabau and Shimer: 

 North American Index Fossils. Invertebrates Vol. I., p. 664. fig. 920. 



2) Koken: I.e. p. 174. 



3) ElCHWALD, I.e. 



4) LoRENz: Beitr. z. Geologie und Palaeontologie von Ostagien. II. Palaeontologischer 

 Teil. P. 104. 



5) Koken: I.e. p. 174. 



