PALEONTOLOGY: J. M. CLARKE 
385 
There is a long lapse in the time record of this line of development for we 
have no present knowledge of the lepad barnacles, in the marine interval 
between the Jura and the Devonian. Certain rare fossils known as Turrilepas 
and Strobilepis have been found in the rocks of the Devonian, Silurian and 
Ordovician; Strobilepis is a singular genus constructed of four vertical ranges 
of plates, two rows broadly triangular and the other two narrow and spini- 
form, and the fact that this Devonian genus is known in but a single specimen 
prevents us from going far in utilizing it in this connection, but its structure, 
a scaly elongated body ending in a single subcircular plate from which the 
vertical ranges diverge, indicates that this plate is terminal at the free end of 
the animal; in other words, a caudal plate. In my previous discussions of 
this genus I have placed Strobilepis and Turrilepas together under the family 
Turrilepadidae, Turrilepas being the older in time and date of description 
and having similar structure except that the vertical ranges are from four to 
six, the scales of each range being more or less interlocked with those ad- 
joining. This fact and the absence, so far as known, of a terminal or caudal 
plate, has led some students to regard Turrilepas as the scaly stalk of a 
lepad rather than the capitulum. However this may prove, I think we may 
be obliged to conceive that there is a less close relation between these two 
genera than their gross structures indicates. 
In the Silurian and Ordovician we have the genus Lepidocoleus now stand- 
ing as the representative of the family Lepidocoleidae and in this the type 
of structure is much simpler than in the genera mentioned. Here is an 
elongate body consisting of but two vertical ranges of plates, which are as 
distinctly 'lateral' in a morphological sense as are the lateralia of the bala- 
nids. These two rows open back and front making two continuous lines of 
suture or dehiscence from the base of attachment to the summit, where there is a 
terminal axial plate. The lateral plates are subequal half -rings or bands and 
the Lepidocoleus was attached to the surface on which it grew by its end and 
obviously by its head. My recorded observations on these structures in the 
Palaeontology of New York, VII, the American Geologist, American Naturalist 
and Eastman-Zittel's Text Book of Palaeontology are sufficient demonstrations 
of these relations. 
Mr. Ruedemann's hypothesis of derivation predicates attachment of the 
ancestral phyllopod by its head and back; primarily by its head, secondarily 
and subsequently by its back. If we limit this fixation to attachment by the 
head alone leaving the rest of the body entirely free and hence subject to much 
more frequent and pronounced lateral stresses resulting from movements, by 
waters or otherwise, from side to side, we call into play only such stresses as 
reasonably seem to have been effective in the development of the Phyllo- 
cardia into Eobalanus. 
The arguments and the causes are of the same category as those which my 
associate has employed. It is, therefore, a matter of special and confirmatory 
significance that these Lepidocoleus forms appear in the Ordovician; that is 
