i62 The Ottawa Naturalist. [December 



of the siphuncle are not at all clearly shown. A label, in 

 Hyatt's hand-writing, however, which accompanies the specimen, 

 states that the siphuncle is "marginal and ventral" as 

 it is known to be in P. Halli. The two fragments marked 2078 

 show neither the external form of the shell, the outline of the 

 transverse section, nor any of the surface markings. One of 

 these is a little more than about one-third of the outer whorl of a 

 specimen which has been worn down in such a manner as to show 

 a longitudinal section of the body chamber and of the last five 

 septa, which average trom five to five and a half millimetres in 

 their greatest distance apart. The other shows scarcely anything, 

 except that the venter is much flattened. 



In the second place, Plectoceras Halli, which seems to be a 

 very characteristic fossil of the Black River limestone, has now 

 been found at two localities near Ottawa city. The first of these 

 is Lot 4, Concession 3, Rideau front, Gloucester, where the 

 specimen referred to in a former paper was found by Mr. Walter 

 R. Billing-s. The second is Mechanicsville, on the Ontario side 

 of the Ottawa River at La Petite Chaudi^re rapids, where a speci- 

 men which shows both the surface ornamentation and the position 

 of the siphuncle remarkably well, was founJ by Mr. J. E. 

 Narraway in October last. 



In the third and last place, on a tablet in the Museum of the 

 Geological Survey there are four fossils from the Black River 

 limestone at St. Ambroise, P.Q., collected by Sir W. E. Logan in 

 1852, that are still labelled '' Lituties undutiis.'" Three of these 

 are apparently small specimens ot Plectoceras Haln. The fourth 

 is clearly neither that species nor Eurystom'ites (or Plectoceras) 

 undatus. It is unfortunately not more than an inch and a quarter 

 in its maximum diameter and does not show the position of the 

 siphuncle, so that it is quite uncertain to what genus it should be 

 referred. A similar but rather larger specimen, which also does 

 not show the position of the siphuncle, has quite recently been 

 found by Mr. Narraway in the Black River limestone at Tetreau- 

 ville. Both of these specimens are apparently gyroceraconic, 

 with laterally compressed whorls, and their surface markings con- 

 sist of thin sharp ribs, with shallowly concave spaces between 



