PULCHELLIID. 143 
only on the outer half of the sides, the spaces between are narrow sulcations 
that cross the venter. The coste cross the venter with undiminished 
breadth and are channeled, but this channel is so shallow that I at first 
thought this must be the young of another species with very broad coste, 
Amm. catillus VOrbigny. The specimen described is just a little older than 
the shell figured as compressissimus by d’Orbigny and ribs begin suddenly to 
bend forward on the last part of the outer volution. Amm. catillus VOrbigny 
may also belong to this genus, but the characters of the young, which alone 
can determine this question, are not known. 
Locality: Escragnolles, France. 
Age: Neocomian. 
PSILOTISSOTIA Hyatt. 
This genus was unluckily considered by me when mentioned for the 
first time” as a member of the Tissotiide. In this I was not led by the 
opinions of Douvillé and Nicklés, but by what I then considered to be its 
true affinities. It has become obvious in studying Paratissotia, which 
approaches it nearest in form and in agreement of the development, that 
this is not a natural association. Nicklés’s plates also show that the sutures 
are similar to those of true Pulchelliide. They are involute forms, smooth, 
and compressed in the earlier stages and having at this time or all through 
the neanic stage a smooth keel that may in older stages become tubercu- 
lated. Costee may be represented by fine folds as in Psil. mariole Nickles, 
until a late age, but when they do appear they are heavy, fold-like, and 
sigmoidal. In this species also a median lateral line of nodes appears. If 
their real affinities are with this family, as they certainly appear to be now, 
they can be accounted for as direct derivations of Psilopulchellia which has 
evolved a keel. The intermediate aspect of species like Pul. defforgesi and 
haugi indicates that the shell did not have a flat ventral area at any stage, 
but was the direct outcome of the evolution of Psilopulchellia. 
This includes besides the type, Psil. chalmasi (Nickles), the following 
species: Psil. mariole, defforgesi, reigi, haugi, Nickles; Pul. defforgesi Nickles 
is described by him as having simply a sharp venter, but its affinity with 
mariolae would bring it into the group and the sharp venter may be 
merely due to the age of the example figured. 
«4 Zittel’s Text-book, p. 590. 
