212 



The maximum diameter of the largest and most perfect specimen 

 knoAvn (that from Sigutlat Lake), is rather more than four inches and 

 and a-half, and the number of primaiy ribs on its outer whorl is thirty- 

 two. The septation of the species is still unknown. 



0. Loganianus belongs to the same setion of the genus as the 0. 

 Astierianus (which is the Ammonites Astierianus of d'Orbigny and 

 Pictet), but its volutions are much more loosely involute, and its 

 umbilicus is far more wide and open. The primarj^ ribs of the outer 

 whorl of 0. Loganianus, also trifurcate on the middle of the sides, and 

 not comparatively near the suture, as they do in 0. Astierianus. 



(Section B. — EvoIut(e.) 



Ancyloceras EfiMONDi, Gabb, 

 Plate 28, figs. 2 and 2a. 



Crioceras (Ancyloceras f) Bhnondi, Gabb. — 1864. Pateontology of California, 



Vol. 1., p. 75, pi. 14, figs. 24 and 

 24(7. 



Ancyloceras Eemondi, Gabb. — ^1869. Idem., Vol. 11., p. 138 and 



213, pi. 24, fig. 19. 



North shore of Cumshewa Inlet, two specimens, the largest of 

 which is figured. 



This species is thus described by Mi-. Gabb, in the first volume of 

 the Palaeontology of California : "Discoidal ; whorls inreasing rapidly 

 in size, flattened on the sides; dorsal surface narrow, convex; ventral, 

 fiat or very slightly concave. Transverse diameter less than half 

 the dorso-ventral. Space between contiguous whorls narrow, but 

 well marked. Surface marked by numerous small flexuous ribs, of 

 about equal size, which arise on the ventj-al margin of the whorls 

 and pass entirely across the back : these ribs are often dichotomous, 

 and occasionally, though rarely, anastomose near the dorsum. In 

 one case I'emains of a few dorsal spines were observed. These were 

 placed in two rows, one on each side of the back. The ventral surface 

 is finely striate transversely'', the striae arching forwards. Of the 

 septum, I htive only been able to see the dorsal and superior lateral 

 lobes, and their corresponding saddles." 



The specimens of A. Remondi from Cumshewa Inlet appear to diflFer 

 only fj'om the Californian type of the species in being much larger, 

 and in the circumstance that their ribs are more distant and very 

 rarely dichotomous. 



