REPORT ON THE TETRACTINELLIDA. 
cxxxv 
Corticata. In 1870 Schmidt ^ proposed the family Ancorinidae to include Sponges with 
“ anchor ’’-shaped spicules, but without sterrasters. The genera enumerated as belonging 
to the family are : — Pachastrella, Sphmctrella, Tetilla, Craniella, Ancorina, and 
Stelletta ; all then defined by Schmidt for the first time. 
In 1875, Carter proposed the group Stellettina as one of the subdivisions of his 
family Pachytragida, which was defined as including “ Sponges more or less corticate, 
with a cancellous, more or less radiated structure, internally well differentiated.” This 
family <^n no longer be maintained, at least not without a revision of the definition and 
a change in the name, as neither are any longer indicative of the Sponges it includes. 
At the same time in its essential features the family is a very natural one ; much more 
so than 0. Schmidt’s. It was subdivided into three groups of subfamily value : — the 
Geodina, Stellettina, and Tethyina (Tetillidse). The Stellettina were rightly distin- 
guished from the Geodina by the absence of sterrasters, a distinction already made by 
Schmidt betw^een his Ancorinidse and Geodiadse. In 1880 Carter,^ recognising the 
essential similarity between Caminus, Pachymatisma, and Erylus, suggested that these 
genera, “ although belonging to the Geodina, should constitute a different group from the 
Geodia proper.” Subsequently, however, in 1883, Carter^ enlarged the contents of the 
group Stellettina by referring to it the genus Erylus, Gray [Stelletta mamillaris and 
Stelletta discophora, 0. Schmidt), although he had previously rightly regarded Erylus as 
a Geodiid genus, and I fail to perceive the reasons for his change of view. The essential 
features of the sterraster are not affected by its form, and are as obviously present in the 
Erylus “disc” as in the Geodine “globate”; it is true, however, that the recurved 
spines which usually terminate the actines of the Geodine sterraster are not present in 
the Eryline, and this difference is connected with a difference in the mode of union of 
these spicules to form the sterrastral layer of the cortex ; but these differences are less 
considerable than those which distinguish the sterraster, whether Eryline or Geodine, from 
all astral spicules of the Stellettidse. 
In 1880 0. Schmidt,^ in adopting the division Tetractinellida, abandons the distinc- 
tion between the families Ancorinidse and Geodinidse as these were defined by him ; 
and quite rightly so, since the contents of the Ancorinidse differ far more from one another 
than from the Geodiidse. The distinction has, however, been quite recently revived by 
Vosmaer;® no reasons are assigned for this step, and the Ancorinidse of Vosmaer are, if 
possible, a more disorderly assemblage of diverse forms than that of Schmidt. Including 
too much and excluding too much, I see no way to accepting it, and prefer to adopt 
Carter’s group Stellettina, at the same time raising it to the value of a distinct family. 
^ O. Schmidt, Spong. Atlant. Gebiet., p. 64, 1870. 
2 Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. vi. p. 137, 1880. 
^ Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. xi. p. 347, 1883. 
* 0. Schmidt, Spong. Meerh. Mexico, p. 60, 1880. 
® Vosmaer, Bronn’s Klass. u. Ord. d. Thierreichs, Porifera, p. 318, 1885. 
