ANIMALS. 141 
former with a rudimentary apophysary system in the form of isolated plates, and the 
latter apparently without any, I have made free to make a trifling addition to Mr. 
Gray’s diagnosis, so as to qualify it for the reception of what appear to be a few 
exceptional cases. 
I purpose, in the next place, adverting to the families herein included in the present 
order, briefly noticing those, and their constituent genera, which are not Permian for 
the sake of comparing them with the Permian groups. 
family STRIGOCEPHALIDZ, King. 
This group is typified with the genus Strigocephalus, and differs from its equivalents 
chiefly in certain of its cardinal characters,—notably its foraminated deltidium, which 
resembles that of Ortiisina; and in its enormously developed ventral median plate, 
cardinal boss or muscular fulcrum, and (sub-marginal, anneliform) loop.’ It seems 
to be confined to the Devonian system. 
Family RaYNCHORIDA, King. 
This group I propose typifying with the genus R/ynchora. It differs from 
Terebratulide 1 generally possessing an area, and a sub-apical foramen; and perhaps 
in its normal members being without a loop. The absence of the last character is to 
a certain extent supported by a figure of Rhynchora spathulata, Wahlenb. im the 
‘Lethea Svecica’ (Pl. XXII, fig. 92), and by another in the ‘Lethea Geognostica’ 
(Pl. XXX, fig. 5d) of the interior of Delthyridea pectiniformis (Tereb. id., J. Sow.), 
both of which appear to be as much divested of an apophysary system as an Orthis, 
or any other Sarcicobrachial palliobranch. The same negative character appears to be 
confirmed by the interior of a Rhynchora costata, Wahlenberg, with which, including 
several other Swedish fossils, I have been kindly supplied by M. Clason, of Fuhrdal, 
in Delacarlia. 
Besides the typical genus (typified with R/ynchora costata, Wahl.), the present 
family embraces Delthyridea,? M‘Coy (the type of which appears to be the Zerebratula 
pectiniformis), and the one next to be noticed. 
1 For a description of the internal structure of Strigocephalus, vide ante, pp. 70-72. 
2 Koenig founded the genus Trigonosemus on a shell named Trigonosemus elegans (Icon. Foss., Sect., 
p. 3, pl. vi, fig. 73). Taking into consideration the external characters of Terebratula lyra, Sow., which 
is also included in the genus, 7’rigonosemus appears to be synonymous with Delthyridea; butas I am totally 
unacquainted with the type just named, it is impossible for me to give a positive opinion on the subject. 
It would be well if the original specimen of Trigonosemus elegans were fully described. 
