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THE VOYAGE OF H.M.S. CHALLENGER. 
or arched above, straight below, protected in front by a broad mucronate plate. Above 
the mouth a penthouse-like projection, usually bifid but sometimes continuous. 
Habitat. — Station 135c, off Nightingale Island, Tristan da Cunha, 110 to 150 
fathoms. 
[South Patagonia, Darwin ; between Patagonia and the Falkland Islands, Captain 
Warren, Hincks.] 
I have followed Mr. Hincks in placing this very peculiar form under a distinct genus, 
quite agreeing with him that it is entitled to take that rank among the Escharidse. 
Mr. Hincks ( loc . cit.) describes the zoarium as composed of two layers, and this was 
the condition in the form described by me in the Brit. Mus. Cat. under the name of 
Eschara gigantea ; but the few fragments contained in the Challenger Collection exhibit 
only a single layer, and from the peculiar aspect of the dorsal surface it is obvious that 
when the layers arc double, they are not inseparably united as in Eschara, but merely 
in apposition, so that in fact Aspidostoma should be regarded as belonging to the 
Hemescliarine rather than to the Escharine type, or that the two layers are formed simply 
by reduplication of the lamina upon itself. 
Mr. Hincks states that “ leaning against the side of many of the cells, a little below 
the upper extremity, there is an avicularium, with a very short, broad, subtriangular 
mandible directed upwards ” ; and also that the “ ooecia are elongate, much depressed, 
shield-like and granulated.” 
He also says that the broad shield-like plate in front of the mouth, or the “ projecting 
lower lip” noticed in the Brit. Mus. Cat., is continued downwards for some distance within 
the cavity ; and that attached to the inner surface of the plate, on a level with the 
margin of the orifice, is a semicircular membrano-calcareous frame into which the oper- 
culum fits. 
§ 2. Primary mouth notched or sinuated below. 
9. Schizoporella, Hincks. 
Lepralia, (pars), Johnst., Busk, &c. 
Escharina (pars), d’Orb. 
Reptoporina (pars), d’Orb. 
Escharella, subgenus Herentia (pars), Smitt, Krit. Forteckn. 
Mollia (pars), Smitt, Ibid. 
Schizoporella, Hincks, Brit. Mar. Polyz. 
Character. — Zoarium erect and bi- or uni-laminar ; or crustaceous and unattached ; 
or adnate. Lower lip with a median notch. Operculum pedunculate, or contracted below. 
