EEPORT ON THE KERATOSA. 



59 



presence alone justifies the establisliment of a new species ; this mainly owing to its 

 histological peculiarities. Apart from the foreign enclosures, its constituent parts are 

 scantily developed transparent ground-mass, and in this latter large vesicular cells 

 of round or more oval form, 0"02 mm. in diameter, not dissimilar to the renowned 

 and still debatable " Schleimzellen " of MoUusca, as Dr. Flemming ^ has drawn them, 

 and thoroughly identical with the vesicular cells of many Desmacidonidse — undescribed 

 indeed hitherto, but undoubtedly very well known to every spongiologist who has 

 had to deal with the representatives of the family just mentioned. A portion of the cortex 

 with such cells is shown in the annexed woodcut. 



But the sponge also possesses some other characters which render it readily dis- 

 tinguishable from other Keratosa, its skeleton recallinar that of 

 a Spongelia rather than that of Cacospongia, and its external shape 

 being perhaps also of some systematic value. The sponge has 

 been found in the form of a thick-walled tube, with very 

 narrow central cavity, ending in a small osculum. The outer 

 surface is rough and provided with rounded tubercles corre- 

 sponding to the prominent secondary fibres. There are in this 

 sponge three kinds of skeletal fibres — (1) gastric vertically directed 

 primary fibres, in most cases more or less loaded with foreign 

 bodies, and on an average 0"2 mm. thick; (2) centrifugal 

 secondary fibres, originating from the primary ones, and in their direction towards 

 the outer surface forming with the last mentioned, if from above, a more or less 

 acute angle, and with an average diameter of 0"1 mm.; and (3) still finer (0"06 mm.) 

 tertiary fibres uniting the secondary and primary ones ; to sum up, this is a kind of 

 skeleton very common in Spongelidae, but exceptionally rare in Spongidge. The secondary 

 and tertiary skeletal fibres proved to be free from any enclosures. Apart from the 

 vesicular cells there are no other histologically or anatomically deviating peculiarities 

 to be stated. 



Colour. — Outer surface dii'ty greyish, parenchyma pale yellowish- white, skeletal 

 fibres straw-yellow. 



Habitat. — Ofi" Port Jackson, April 1874 ; depth 7 fathoms. 



Fio. 2. — Cortex of Cacospongia 

 vesicnlifera. a, pavement 

 epithelium of a subdermal 

 cavity ; b, vesicular cells. 



Cacospongia procumbens, n. sp. (PI. VI. fig. 6). 



This species — a Sarcotragus in the sense of Oscar Schmidt — possesses a very curious 

 skeleton. In Cacospongia vesiculifera we have had to deal not only with primary and 

 secondary, but also with tertiary skeletal fibres ; here there are not even primary and 

 secondary ones. The sponge has been found in the form of a crust, and its supporting 



' Die Bindesubstanz der Mollusken, pi. i. 



