SYSEHMATIC DESCRIPTIONS: 
MAMMITIDA.* 
This group in my chapter on Cephalopoda in Zittel’s Text-book con- 
tained a number of keeled families, in which either the keel was preceded 
by a median line of tubercules, or, if this stage were omitted, the smooth 
keel arose upon the venter in forms that were apparently closely allied to 
the more primitive genera having these tuberculated keels. The Mam- 
mitida included Mammitidee, Peroniceratidee, Prionotropide, Hystato- 
ceratidee, Lenticeratidee, and Tissotiide. To these I propose to add now 
the Mojsisoviesiidee, Buchiceratidee, Pseudotissotiidae, Kulophoceratidee, Sphe- 
nodiscidee, and Coilopoceratidze. 
MOJSISOVICSIIDAE Hyatt. 
The single genus and species described below can not be even pro- 
visionally included in any of the groups to which it is supposed to be 
nearly related, and the following discussion of its generic affinities shows this 
conclusively. The dorsal sutures are not yet known, and this is the only 
defect in the evidence that establishes it as an independent group, probably 
belonging to the parent stock or stem of the Pachycampyli. 
MOJSISOVICSIA Steinmann. 
The interesting species used as the type of this genus has a form 
which is similar to that of Agassiceras of the Lower Lias in being smooth 
and discoidal, with flattened sides, narrow umbilical zones and rounded 
venter. The section is what I have called helmet shaped, like Agas. striar- 
ies. It differs in having no raised line or keel, and therefore comes a little 
nearer to Psiloceras. The sutures bear a similar interpretation, since, 
although these are very immature, there are four lateral bifid saddles with 
“A penciled note at the top of this page of manuscript says ‘‘ Revise list.’? Just what changes 
the author would have made can not be known, but it may be inferred that Lenticeratide was 
dropped as an abandoned family, and that possibly Coilopoceratide was assigned to another super- 
family. It is obvious that his conception of the group Mammitida had become very different from 
that expressed by him in Zittel’s Text-book.—T. W. §. 
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