ANIMALS. 13 
(Lymnorea mamuullosa, Lamouroux), but it does not display the large oscula on the 
summit of the mammille, characteristic of the latter. The want of large excurrent 
openings in this species has caused its removal from the genus Jd/axon, in which it 
was formerly placed. 
Mammillopora mammillaris occurs sparingly in the Shelly Limestone at Humbleton 
Hill. 
Genus Zragos, Schweigger. 
Diagnosis.—* Stirps e fibris densis, subgelatinosis ; superficies ostiolis distinctis.”” 
(Schweigger.) 
The type of this genus is the A/cyonium incrustans of Esper, which belongs to the 
order Halinida. There is considerable doubt as to whether the following two Sponges 
ought to be placed in it. 
TRAGOsS TUNSTALLENSIS, King. Plate II, fig. 5. 
Diagnosis.—Form irregularly infundibular. Swmmit expanded and slightly exca- 
vated. Margin of the cavity irregularly lobed. Outer surface uneven. Substance fibrous, 
with numerous, small, excurrent passages. 
The usual size of this Sponge is half an inch in height, and three quarters in 
width. In its fibrous texture it resembles the Zragos patella, figured by Bronn in the 
‘Lethzea Geognostica,’ pl. xvi, fig. 3. 
It is occasionally found in the Shelly Magnesian Limestone at Tunstall Hill. 
Tracos Binneyi, A7ng. Plate II, fig. 6. 
Diagnosis.—Infundibuliform ; slightly excavated at the summit. Swrface porous, 
and irregularly tuberculated. 
This is a larger species than the last, occasionally measuring an inch and a half in 
width, and two inches in height. It appears to have been variable in its relative 
proportions, as some specimens are much less in height than in width; they have 
somewhat the appearance, however, of having been depressed by superincumbent 
pressure. None of the specimens examined show any excurrent openings on the 
outside, but it is suspected that these, as in many recent cup-shaped Sponges, were 
situated within the cavity: this part, however, is in general so filled up with mineral 
matter and casts of shells, that it is impossible to offer any decided opinion on this 
pomt. Where the outside is pretty clear of the investing mineral matter, there may 
be seen a few small pores, which, it may be safely concluded, were the openings of the 
' Handbuch der Naturgeschichte der Skelettlosen ungegliederten Thiere, p. 422, 1820. 
