PSEUDOLIOCERAS. 83 



a flattened middle, indicating that in extreme youth there was less occlusion. The 

 suture-line (Plate A, fig. 22) shows a siphonal lobe with short, somewhat divergent 

 terminal points ; the siphonal saddle is rather large, encroached upon by some 

 digitations from the lobes, and unequally divided by a fairly well-developed 

 accessory lobe; the interior portion of this saddle is larger and deeper. The 

 superior lateral lobe is large, with several lateral digitations and some slight 

 amount of trif urcation at the end ; the superior lateral saddle is rather deep and 

 narrow ; the inferior lateral lobe is quite small in proportion to the superior ; the 

 first auxiliary lobe is fairly well developed, and digitations seem to indicate the 

 presence of a whole series of smaller auxiliary lobes. The position of the septa 

 with regard to one another indicates a medium-sized chamber, not so large as in 

 Ludwigia, but rather larger than in Lioceras. 



Remarks. — This genus appears at first sight to be intermediate between 

 Harpoceras and Lioceras, to both of which it has very considerable similarity in 

 form. From Harpoceras it may be separated by the following characters : — It 

 does not possess such a pronounced hollow carina, its radii have not the strongly- 

 marked sickle-shape, with its sweeping curve on the outer area, and its long 

 forward bend on the ventral area; its ribs are only developed on the outer 

 lateral area, and are then broader, more distant, and more regularly rounded ; its 

 suture-line has a broader siphonal lobe, with shorter, more divergent terminal 

 points, a smaller inferior lateral lobe, and a greater number of auxiliary lobes. 

 From Lioceras, which it particularly resembles in the character of its ribbing, it 

 may be separated by its having a hollow instead of a solid carina, a straight and 

 upright inner margin, and a different suture-line. The sutures have a larger 

 accessory lobe in the siphonal saddle, a smaller inferior lateral lobe, and a less 

 distinct series of auxiliary lobes. 



The genus Pseudolioceras contains at present but few species, and its vertical 

 range is not very great. The earliest form is probably Pseudolioceras lythense 

 (Young and Bird), which occurs in the Upper Lias. A direct descendant of this 

 is very probably found in Ps. compactile (Simpson), which occurs in the lower 

 part of the Cotteswold Sands with a variety of Hildoceras bifrons (Section VI, 

 p. 45), and at what is perhaps a slightly higher horizon in the Sands, with Lytoc. 

 sublineatum (Section VII, p. 46) ; but only lately have I found it in the 

 Striatidum-be&s. In the Opalinum-zone at Haresfield (Bed 15, Section V, p. 43) 

 and at other places other specimens of the genus occur which must be considered 

 as varieties of Ps. Beyrichi (Schloenbach). (This species is doubtless a direct 



deal with that question, because other characters, namely, ribbing, suture-line, &c, have also varied 

 sufficiently. 



This hollow-keel structure seems to be little, if at all, known in England. For further information 

 concerning it the works of Quenstedt, Waagen, Haug, Vacek, and Denckmann may be consulted with 

 advantage. 



