G. C. Crick — Orthocerata from North China. 



483 



a common species in the Black Eiver Limestone (Ordovician) of 



New York State. 



The original of Fig. C in our Plate XXII is referable to the same 

 genus, and possibly also to the same species. 



It is of interest to mention that the matrix contains several small 

 Brachiopods respecting which Mr. Buckman (who kindly examined 

 them at Dr. Woodward's request) says, " The general appearance 

 suggests Orthis {Balinanella) testudinaria, Dalman, an Ordovician 

 species." 



A second species is represented by a photograph of a section of 

 a fragment (Plate XXII, Fig. B), and a rubbing of another specimen 

 about 25 centimetres long, displayed in section on the surface of 



Fig. 2.—Actinoeeras imhricatum, Hisiuger, sp. a, fragment of a cast, sliowing 

 the disposition of the septa on the siphuucular aspect ; h, section of a smaller 

 individual, shomng the large nummuloid siphuncle sc, and the septa s ; 

 c, transverse section, showing the position of the siphuncle (si) and its 

 diameter between the necks of the septa, a and h of the natural size ; 

 c, reduced half. Silurian (Upper Ludlow) : Island of Gothland, Sweden. 

 (After Foord.) 



a slab. Although the relative proportions of the parts of the shell 

 — the relatively wide siphuncle and the very shallow chambers — 

 agree fairly well with those of Actinoceras imhricatum, Hisinger, sp.,^ 

 from the Silurian (Upper Ludlow) of the Island of Gothland, 

 Sweden (see Figs. 2a-c), it seems scarcely likely that an example 

 of this species could be so worn down as to expose the siphuncle 

 for a length of 25 centimetres. I therefore venture to suggest that 

 the specimen may belong to Hall's genus Gonioceras,- which at 

 present is known only from the Ordovician rocks of North America, 

 and possibly also from Norway (see Figs. 3a, b). 



1 Hisinger: Anteckn. i Physik och Geognosie, Haft, v, p. 112, tab. iv, fig. 4. 

 See also A. H. Foord, Cat. Foss. Ceph. British Museum, pt. i (1888), p. 180, fig. 24. 

 » Nat. Hist. N. York, pt. vi, Palajoutology, vol. i (1848), p. 54. 



