EcHINoDERMATA. | LOWER PALAZOZOIC RADIATA. 59 
‘madreporiform tubercle, marking the posterior side and forming the external termination of a peculiar organ 
termed the ‘sand canal’ extending from thence to the arterial circle round the mouth. The genital 
openings pierce the bony circle round the mouth. The mouth has no teeth; the cesophagus is short, 
and two large czeca extend into each ray, exposing the chyle to the veins, which latter communicate with 
a large circular yenous trunk surrounding the mouth, and communicating by a vertical muscular tube, 
or heart, with a smaller arterial circle also surrounding the mouth and giving out branches to the mouth, 
to the intestine, others running between the ambulacra supplying the suckers, and perforating the in- 
tegument at the tips of the ambulacra to supply the external membranes. The nervous system is distinct, 
one cord runs round the mouth, giving off three branches to each ray, one running between the ambulacra 
to the tip, where, according to Ehrenberg, it dilates to form a bulb or optic nerve, to supply a bright 
red point at the end of each ray, usually considered to be, in consequence, a true eye; the other two 
nervous branches supplying the viscera. The sexes of all the Starfishes are in distinct individuals, the 
ovaries in the one case, and testes in the other, forming bunches of slender czeca round the cesophagus, 
two at the origin of each ray. 
The following notice of the Paleozoic Starfishes has been contributed by Prof. KE. Forbes. As the 
specimens belonging to the University Collection have been figured by the Geological Survey, it has not been 
thought necessary to refigure them. Before I was aware Professor Forbes had described them it seemed to 
me that the U7. Ruthveni and U. Hirudo, as well as the similar American species, might be easily separated 
from the great star-fishes forming the recent genus Uvaster, by their small size and much more simple 
skeletons, and I had named the genus Uvasterella in my MSS. The U. Primevus I thought generically 
distinct from the other two, as the rays were not contracted at base &e. ; and I had named it Palasterina, from 
its resemblance to the recent genus Asterina. 
‘“‘True starfishes have rarely been met with in the older rocks. When they do occur, however, they 
are not likely to be overlooked, as their forms and structure cannot easily be confounded with those of 
the other radiata. At the same time, the fragility of the existing species and the difficulty attending 
their preservation entire, after death, reduce the chances of our finding them frequently in the fossil state. 
Such as do occur in Palzozoiec rocks haye a singular resemblance to existing forms, especially to those 
species which are characteristic of Northern seas. Hence it is convenient to retain them in known genera ; 
for although parts may have been lost, and textures disappeared, which might have warranted their generic 
separation, there is nothing remaining to us of their organization which would not be consistent with that 
of existing Asteriadw of the generic groups to which they are here referred. i 
Genus. URASTER (Agassiz). 
UrasterR Rutuvent* (F orb.) 
ef. —Forb. Mem. Geol. Surv. Dec. 1. t. 1. f. 1. 
“Sp. Ch.— Disk small; arms rounded, very long, linear-lanceolate, subearinate. Upper surface reticulated; 
interspaces irregular ; under surface marked with the impressions of the double series of linear ambulacral 
ossiculze, each of which is slightly curved. 
“The back and upper surface of arms of this species were probably covered with close set fasciculi of 
small obtuse spines. Disk to ray as 1—5. Breadth of ray 03. Breadth of Disk 3 inch. Length of ray 15. 
UrAsTER? HIRUDO (Forb.) 
Ref.—Forb. Mem. Geol. Surv. Dec. 1. t. 1. f. 4. 
“« Sp. Ch.—Disk very small; arms tapering, linear lanceolate, acuminate, contracted at their bases. Upper 
surface with radiating series of reticulated spinous bundles, placed very regularly, so that each ray appears 
* Named in compliment to the zeal and intelligence of Mr. John Ruthyen, of Kendal, who has collected the greater 
part of the Westmoreland fossils—and is well acquainted with the structure of his native county. 
12 
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