M. K. A. Zittel on Fossil Tetraclinellidee . 
311 
Tethyopsis, Zitt. 
Of irregular, nodular, or clavate form. Skeleton composed 
chiefly of very large, straight or slightly curved, bacillar 
spicules, as much as 5 millims. long, sharply pointed at both 
ends, which, being laid together in a parallel direction, give 
the interior of the sponge-body a radiate structure. The sur¬ 
face is formed by a layer of smaller three-pronged anchors, the 
long shaft of which is turned inwards. The three prongs are 
generally equally developed, and spread out horizontally 
with their points a little recurved. Among these large an¬ 
chors there are scattered smaller ones, in which the three 
short prongs are recurved like hooks. The cortical anchors 
are further associated with small somewhat curved bacillar 
spicules and with isolated quadriradiates. 
Although the anchors, quadriradiates, and small bacillar 
spicules just described are chiefly concentrated at the surface, 
they are also to be observed in the interior of the sponge-body, 
but only in radial lines, therefore probably as the lining of 
canals. 
This form comes very near to the living Tethya cranium , 
liisso, and the allied species to "which Carter* would limit the 
name Tethya , whilst O. Schmidt has proposed for them the 
designation Tetilla. I have, however, hesitated to unite the 
fossil form with the living ones under the same generic name, 
as the superficial anchors in Tethyopsis rather resemble those 
of Geodia and Stelletta than those of Tethya lyncurium. 
At present I know only a single specimen of this species, 
for which I propose the name of Tethyopsis Steinmanni. 
Pachastrella, Schmidt. 
This genus was established in 1868 by Oscar Schmidt 
(‘ Spongien der Kiiste von Algier,’ p. 15), and characterized 
as follows :—“ ACompaginean without epidermis, with spicules 
of the character partly of the Compaginese, partly of the Cor- 
ticatae.” In the Atlantic sponge-fauna two other species (P. 
abyssi and connectens , Schm.) are figured ; but we are indebted 
to Carterf for the first sufficient and detailed characterization 
of the genus, and for satisfactory figures of the skeletal 
elements. 
According to him, Pachastrella embraces massive, nodular 
or lamellar, frequently parasitic or incrusting sponges, without 
determinate external form, and without any special cortical 
* Ann. & Mag. Nat. Hist. ser. 4, vol. viii. (1871) p. 103. 
t Ann. & Mag. Nat. Hist. ser. 4, vol. xvi. (1875) p. 68, and vol. xviii, 
(1876) pp. 406-410. 
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