34 G. LINDSTRÖM, THE ASCOCERATIDAZ AND THE LITUITIDA. 
Only the Ascoceras stage has been found. 
Shell laterally compressed and consequently with elliptico-oval section. The neck 
is sigmoidaly curved, first bent in an obtuse angle towards the straight dorsal side and then 
again, near the aperture against the convex ventral side. ”The aperture is trilobate, with 
a broad tonguelike lobe from the dorsal side and two small blunt lobes on both sides of 
the semicircular sinus of the ventral side. The margin of the aperture is thickened 
by a weal. 
The sculpture consists of fine, imbricate, transverse lines more or less closely set 
and they are crossed by fine, often indistinet longitudinal folds, forming sometimes together 
a fine network. 
There are four sigmoid septa, which in their innermost curve increase in breadth 
the higher they are situated. "The first sigmoid septum is 3 millim. broad, the fourth 
nearly 6 millim. Exceptionally a specimen, delineated in fig. 44, has five distinct septa. 
There is no intermediate septum between the thick septum of the truncature and the first 
sigmoid one. The siphuncle is placed close to the ventral side and consists of four num- 
muloid elements, of which the oldest is as large as the two following. The neck of the 
septa is curved downwards. The aperture of the old siphuncele is closed in no inordinary way. 
Length 41 millim., largest diam. 9 millim., shorter diam. 6 millim. 
Although there may be some trifling deviations, as in the shape of the large lobe of 
the aperture, I have joined the Gotland specimens with the Bohemian form. The more 
elongated Bohemian type has not yet been met with in Sweden and the variety curta is 
also very rare, about seven specimens having been hitherto collected. The Bohemian spe- 
cimens have 6 septa and are as a rule larger than ours. 
Gen. Choanoceras n. 
(Deriv. yoavos a funnel.) 
Syn. 1888. Choaniceras Linpstr. List of Fossil Faunas of Sweden p. 7. Name only given, without description. 
Shell resembling a faintly curved Orthoceratite with the lower extremity truncated 
and conically pointed. Aperture probably simple. Body chamber very large, occupying 
almost ”/,, of the whole shell. Septa from four to six, formed as a pointed oblique fun- 
nel. In the younger specimens with only four septa, these are all equally well developed. 
In the more advanced or adult specimens there are six septa, of which three are com- 
plete and the three youngest ones incomplete or lacunose. The siphunele is nummuloid 
in the older, cylindrical in the younger and the necks of the septa hooklike and strongly 
recurved. 
This interesting genus, which for the present consists of only a single species, is 
the exact contrast to Ascoceras in the arrangement of its lacunose septa. In Choanoceras 
they are very poorly developed, whereas in Ascoceras their dorsal portion attains a size many 
times exceeding that of the ventral portion. On the concave side the septa are parallel and 
equidistant, on the convex side again they approach more or less. In the three youngest 
septa there is an open or empty space. As to the position of the lacunose septa it may 
