Cote—On Hemitrypa hibernica. 133 
layers in Hemitrypa were, in a broad way, correctly appreciated by 
the founder of the genus. 
M‘Ooy (2, pp. 204-5), who probably had much better material 
in his hands, accepted the genus, describing it as “‘ covered with 
an external (imperforate ?) sheath.” While referring some frag- 
ments to H. oculata, on account of the smallness and roundness of 
the openings in the external sheath, he established a new species, 
Hemitrypa hibernica, attributing the specific name to a manuscript 
note of Scouler. He states (2, p. 205) that this species has an 
external poriferous face, meaning, I presume, that the pores, or 
openings of the zocecia, are on the face covered by the ‘‘ sheath.” 
He notes that there are about three pores to the length of a 
fenestrule, and adds :—“ External sheath, nearly smooth, marked 
externally with faint, equidistant strize, which coincide with the 
interstices of the internal net-work, and enclosing between them 
two alternating rows of large, rounded, or obscurely hexagonal 
depressions, coinciding with the openings of the internal net-work.” 
This description is vague and only partial; we should scarcely 
conclude from it that every pair of rows of “depressions” in the 
sheath overlies one of the rows of fenestrules (‘‘ openings”’) in the 
internal net-work ; but this is probably what is meant, and is 
what specimens in the Griffith collection show. It is scarcely 
likely that M‘Coy observed that the “ depressions” corresponded 
to the ‘‘ pores” or zocecial openings, or he would have expressed 
the fact more clearly. 
The only differences between H. hibernica and H. oculata, 
_ Phill., are in the large size of the openings or “ depressions” in 
the sheath of the former, and the squarer form of its fenestrules; 
and for these differences we must trust Phillips’s figure for the 
present. 
M‘Coy was struck with the resemblance of the internal mesh 
of H. hibernica to Fenestella membranacea, Phill., and, in describing 
that species (2, p. 202), says, “I have recently seen a specimen 
exhibiting traces of the external sheath of Hemitrypa.” Further- 
more, he adds, with keen insight (2, p. 200), “ Hemitrypa is 
possibly only the perfect state of Fenestella.” 
W. Lonsdale (3, p. 183), about the same date, described a third 
species, H. sexangula ; but he believed it to be really identical with 
