Miscellaneous. 
459 
the surface of attachment tor the rib, instead of occupying nearly all 
the breadth of the lateral surfaco of the centrum, is, on the contrary, 
of but small extent. The length being 100, the breadth is 159 and 
the height 112. 
The genus Colymbosaurus, belonging to the family Elasmosauridae, 
known only from the Cretaceous in England, is represented in the 
upper part of the Kimmeridgian at Boulogne by a species, Colymbo¬ 
saurus Dutertrei, Sauv., the cervical vertebrae of which are remarkable 
by the form and size of the articular apophyses. The centrum is 
elongated ; and its three diameters are nearly equal; the lower sur¬ 
face, scarcely excavated in the direction of its length, is divided by a 
narrow keel; the pleurapophyses, intimately soldered to the centrum, 
spring from it in the form of a flattened plate ; the articular surfaces 
are flat and nearly circular in form ; the praezygapopl^ses are in the 
form of rounded ribs ; the postzygapophyses are in the form of 
plates; the neural spine is much compressed in the form of a thin 
plate ; the medullary canal is very narrow and rounded.— Ann. 
des Set. Nat. ser. 6, tome viii. 
The Nebaliad Crustacea as Types of a new Order. 
By Dr. A. S. Packard, Jun. 
The Nebaliadse, represented by the existing genus Nebalia , have 
generally been considered to form a family of Phyllopod Crustacea. 
Metschnikoff, who studied the embryology of Nebalia, considered 
it to be a “ Phyllopodiform Decapod.” Besides the resemblance to 
the Decapods, there is also a combination of Copepod and Phyllopod 
characteristics. The type is an instance of a synthetic one, and is 
of high antiquity, having been ushered in during the earliest Silurian 
period, when there were (if we regard the relative size of most 
Crustacea, and especially of living Nebalice ) gigantic forms. Such 
was Dithyrocaris, which must have been over a foot long, the cara¬ 
pace being seven inches long. The modern Nebalia is small, about 
half an inch in length, with the body compressed, the carapace bi- 
valved as in Limnadia , one of the genuine Phyllopods. There is a 
large rostrum overbanging the head ; stalked eyes ; and besides two 
pairs of antennae and mouth-parts, eight pairs of leaf-like, short, 
respiratory feet, which are succeeded by swimming-feet. There is 
no metamorphosis, development being direct. 
Of the fossil forms, Ilymenocaris was regarded by Salter as “the 
moi’e generalized type.” The genera Peltocaris and Discinocaris 
characterize the Lower Silurian period, Ceratiocaris the Upper, 
Dictyocaris the Upper Silurian and the lowest Devonian strata, 
Dithyrocaris and Argas the Carboniferous period. Our existing 
north-eastern species is Nebalia bipes (Fabricius), which occurs 
from Maine to Greenland. 
The Nebaliads were the forerunners of the Dccapoda, and form, 
we believe, the type of a distinct order of Crustacea, for which the 
name Pliyllocarida is proposed. — American Naturalist, Feb. 1879. 
