The Fossil Elasmobranch Fishes. , Bs) 
From the same locality the Museum contains four species of Rhino- 
batus, and the type specimens of three; the fourth (R. maronita) 
being in the Geneva Museum. This is the only genus of the Rhino- 
batida in the collection. The Rasip@ is also only represented by 
the genus Raja. The type specimens of three species, also from the 
Lebanon, are in the collection, one (R. primarmata) being here first 
described and figured. The well-known dermal tubercles from the 
Norwich Crag, named by Agassiz Raja antiqua, are now referred to 
the common Thornback (R. clavata). 
The Psammopont1pm, here classed with the Rays, were referred 
by Agassiz to the Cestraciont group. The family is extinct and only 
known by the dentition, and this shows “that the two rami of the jaws 
were evidently placed in the same straight line—a fact indicating a 
much depressed body, like that of existing Rays.” It comprises the 
genera Copodus and Psammodus. The former consists of eleven 
species, of which all the type specimens are in the Museum; the 
latter of six species and some of the types. One new species (P. 
salopiensis) is described. The species are all Carboniferous, and the 
best known, P. porosus, is now referred to P. rugosus. 
The Mynioparipm come next with eight species of Myliobatis, all 
Tertiary. Only those known by the dentition are catalogued, and 
the published British species are reduced in number. The upper and 
lower series of connected dental plates are distinguished, the upper 
series are arched antero-posteriorly, the lower series being flat; and 
the barbed spines referred to the genus are generically indeterminable. 
One new species (IM. (?) tumidens) from the Red Crag and also a new 
species of Rhinoptera (R. Daviesii) from the London Clay are described. 
The dental plates named Zygobatis by Agassiz were referred to this 
genus by Dr. Giinther in 1880. Aetobatis is allied to the last-named 
genus, but distinguished by the absence of lateral teeth. The long 
familiar Cretaceous genus Ptychodus, and its many species, once 
prominent members of the Agassizian group of Cestracionts, is placed 
by the author in this family, he being the first to discover, by the 
arrangement of the dentition, its natural affinity to the Rays. The 
teeth were numerous in each mouth, and arranged in many longitu- 
dinal and transverse rows. The median antero-posterior row in one 
jaw is very small, the row on either side being much larger ; 
in the other jaw the teeth of the median row are large, and those 
on each side smaller. Péychodus is only known by the teeth and 
vertebre. The vertebree are “apparently ‘cyclospondylic’ in 
structure,” and were found in immediate association with teeth of 
P. decurrens in a block of chalk. Many of Agassiz’s types are in 
the collection; and there is one new species, P. multistriatus. The 
fin-spines and rays referred to this genus by Agassiz do not even 
belong to the same subclass. Of the T'rRyconmpa, the only genus in 
the collection is Cyclobatis, with two species and the type specimens 
of each. This ends the Tectospondylic section. 
Only six families are assigned to the suborder Asterospondyli, but 
the genera and species are many. The Noripanip# is the first 
family, ‘‘its relationships,” according to the author, “ being 
