1873.j oom [Morse. 
pods the collar covers and protects the arms, which, however, 
may partially project, asin Terebratulina and Lingula, and wholly 
so in Rynchonella psittacea, as I observed last year.! 
Furthermore this pallial membrane, or cephalic collar of the 
Brachiopods, is not to be compared to the mantle in the Mol- 
‘ lusea, as pointed out by Dr. Carpenter in 1854. In a paper on 
the peculiar arrangements of the sanguiferous system in Tere- 
bratula, and other Brachiopods,? he says : “The membrane 
which is commonly spoken of as the mantle, and which may be 
stripped from the shell by the use of sufficient force to overcome its 
adhesions, must, I maintain, be considered as really its inner layer 
only ; for I find that an outer layer exists, so intimately incorporated 
with the shell as not to be separable from it without the removal of 
its calcareous component by maceration in dilute acid. When thus 
detached, this outer layer is found to be continuous with the mem- 
brane lining the perforations in the shell.” I have observed that 
when the test® is removed in Lingula pyramidata, the perivisceral 
cavity is often exposed, of such extreme tenuity is the inner lining 
membrane. 
From a figure and description given by W. Baird,‘ of a peculiar worm case 
Terebella flabellum, the cephalic collar might have had the proportion of many 
Brachiopods, in being broader than long. He describes the orifice of the tube 
as being circular,-and says, “the most characteristic feature, however, in the 
structure of this tube, is the fan-shaped expansion of filaments at its upper 
orifice. This orifice is circular, and has on its dorsal surface a projecting lip, or 
kind of hood, which extends beyond the mouth for a short distance, whilst from 
the ventral side springs another lip or hood.”’ 
Dr. Dawson® represents the worm case of Vermilia serrula from the Gulf 
of St. Lawrence, in which there is a marked thoracic enlargement. 
In a few worms only, do we find dorsal scales, as in Polynoe, or 
posterior and ventral scales, as in Sternaspis, and when these occur, 
they are chitinous, as in Discina. In Brachiopods the dorsal, and 
ventral shells, or plates, are unlike anything we know of in worms. 
Their composition and structure, however, their dorsal and ventral 
1 American Journal Science and Art, Vol. 1v., Oct., 1872. 
2 Proc. Royal Soc., London, Vol. vit., p. 82. 
3 The test of this species, when dried, wrinkles and folds together like the scute 
of Lepidonotus. , 
4 Journal Linnzan-Soc., Vol. viit., p. 157, pl. 5, figs. 1, 2. 
5 Canadian Naturalist, Vol. v., p. 24. 
