INVERTEBRATE PALAEONTOLOGY. 4(59 



row of .small, late rally -com pressed nodes, or slight prominences, alternately 

 arranged with their longer diameters parallel to the direction of the periph- 

 eral curve; aperture compressed-sagittate; outline of lip unknown; sur- 

 face showing obscure sigmoid lines of growth, with a row of very small nodes 

 or tubercles, about one-third of the way across from the peripheral margin, 

 and another of somewhat larger ones, near the umbilicus, on each side, those 

 of the former series numbering about two to each one of the latter. 



Size of mature, fully-developed specimens unknown. Greatest diameter 

 of an imperfect example, consisting entirely of septate volutions, 6 inches; 

 convexity of same, 1.72 inches. 



Septa crowded, in large specimeus complex, with comparatively rather 

 short branches; siphonal iobe a little wider than long, but with body slightly 

 longer than wide, provided with three oppositely-arranged lateral branches 

 on each side, the two terminal of which are much larger than the others, and 

 each ornamented with some five or six palmately-spreading, more or less 

 sinuous and digitate branchlets ; first lateral sinus as long as the siphonal 

 lobe, but narrower, with an extremely narrow body, and deeply divided at 

 the end into two nearly equal bi- or trilobate terminal branches, with sinu- 

 ous margins, and provided with two principal, more or less sinuous, lateral 

 branchlets, one of which on the siphonal side is much larger than the others ; 

 first lateral lobe about as long as the siphonal lobe, and still narrower than 

 the first lateral sinus, a little obliquely curved, and tripartite at the extremity, 

 the divisions being short, with sinuous and digitate margins, while it also 

 supports two or three similar short lateral divisions on each side; second 

 lateral sinus shorter and narrower than the first, with a very contracted, 

 zigzag body, provided with two short, alternately-disposed, sinuous, lateral 

 branches on each side, and two short, diverging, bifid, and sinuous terminal 

 divisions; second lateral lobe a little wider and longer than the first, trifid at 

 the extremity, with three alternating lateral branches, of which the two next 

 to the terminal ones are larger and more deeply divided than the others ; 

 third lateral sinus of much the same size and form as the second, excepting 

 in minute details ; third lateral lobe longer than the second, but of about the 

 same breadth and very similarly branched ; succeeding lateral lobes and 

 sinuses becoming at first abruptly, and then gradually and regularly smaller 

 and less complex in their divisions toward the umbilical margin; the sinuses 

 being all much contracted near the middle, and more or less bifid at their 



