400 Mr. A. H. Foord o?i " Orthoceras 



of specific distinction ; and even when the apex is fortunately 

 preserved, as in Holm's species, I hold that such structures, 

 connected as they admittedly are with embryonic development, 

 have too wide an import to be employed in such a way. 



Horizon. Orlhoceras-lAm&QtoxiQ ( = Arenig*). 



Localities. Uitby, near Lake Siljan, and Kinnekulle Hill 

 (Westrogothia), Sweden ; Reval (Esthonia), Russia. 



Orthoceras hinnehullense, sp. nov. 



Sp. char. Shell elongate, tapering at the rate of 1 in 9. 

 Cylindrical in cross-section. The septa direct, distant about 

 ^ the diameter, strongly arched, their convexity about f that 

 of their diameter. Siphuncle a little eccentric, about 3 lines 

 in diameter where the shell has a diameter of 21 lines. Test 

 ornamented with regular, direct, flattened, transverse riblets, 

 divided by narrov/ interspaces. Body-chamber unknown. 



Eemarhs. The most characteristic feature in the present 

 species is the sculpture of the test, which is beautifully pre- 

 served on most of the specimens that have come before me. 

 The figure (2, h) will enable the reader to realize the sculpture 

 of the shell much better than a verbal description can do. It 

 is necessary, ho v/ ever, to state that the riblets vary in width, 

 so that in some places nearly five of them are contained in 

 the space of 1 line, while in others, especially at the larger 

 extremity of the shell, only about two and a half are required 

 to fill that space. Ordinarily about four to four and a half 

 are contained in one line. These measurements include the 

 interspaces. It will be understood from this that the orna- 

 mentation of the test is visible to the naked eye. 



The dimensions of the largest specimen in the national 

 collection (fig. 2) are as follows: — length 11 inches, greatest 

 diameter 2 inches, least diameter 1 inch. Septa about ^ inch 

 apart, but becoming a little closer near the smaller extremity 

 of the shell. 



The very characteristic ornamentation of this species sepa- 

 rates it from all other Ordovician species known to me. 



Horizon. Orthoceras- Limestone ( = Arenig) . 



Localities. K innekuUe Hill (Westrogothia), and Oeland, 

 Sweden. 



* See a valuable paper by Prof. F. Schmidt, of St. Petersburg, " On 

 the Silurian (and Cambrian) Strata of the Baltic Provinces of Russia, as 

 compared with those of Scandinavia and the British Isles," in Quart, 

 Journ. Geol. See. vol. xxxviii. p. 614 (1882) ; also J. E. Marr, 'On the 

 Classification of the Cambrian and Silurian Rocks,' pp. 74 and 82 

 (1883). 



