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THE VOYAGE OF H.M.S. CHALLENGER. 
Collectella avita, 0. Schmidt. 
Gollectella avita, O. Schmidt, Spong. Meerb. Mexico, p. 86, pi. v. fig. 1, 1880. 
Sponge. — Knob-like, with a somewhat flattened summit, on which vertical canals 
open. 
Spicules. — 1. Megascleres. 1. Desma, tetracladose, epactines highly tuberculated, 
tubercles extending up to the origin of the epactines. 2. Calthrops. 3. Dichotrisene. 
II. Microscleres (?). 
Habitat . — West Indian Islands, lat. 25° 33' N., long. 84° 21' W. 
Remarks. — 0. Schmidt regards this sponge as presenting an instance of a passage 
between the Lithistida and the Choristida, the calthrops resembling that of Pachastrella; 
this spicule according to Schmidt is not present as a foreign inclusion, but is proper to 
the sponge, through all parts of which it occurs equally distributed. 
It is to be inferred from the description, however, that the specimen is merely a 
skeleton without soft parts, and while it is probable that the calthrops have not been 
washed in, it is by no means so certain that they have not been introduced by some 
excavating Pachastrellid sponge. Unfortunately I can add nothing in the way of 
direct observation on this point, for the specimen seems to be lost ; Mr. Fewkes informs 
me that none bearing its name is to be found in the collection returned by Schmidt 
to Agassiz. 
Geodia {f) stellosa, Czerniavsky (omitted from p. 274). 
Geodia stellosa, Czerniavsky, Bull. Soc. Nat. Moscou, liv. p. 281, pi. iv. figs. 1-20, 1880. 
Isops {?) stellosa, Vosmaer, Nied. Arch. f. Zool., Suppl.-Bd. i., 1882. 
Vosmaer compares this sponge with Isops pallida, Vosmaer. I have not been able 
to refer to the account of it given by its describer, nor to the definition of the new 
genus Stellogeodia by the same author. 
