TRANSACTIONS OF SECTION D. 779 
perfectly preserved, they are well-marked tri- and quadriradiate spicules similar to 
those of other calcareous sponges.! They are closely packed together, the rays 
being bent to adapt them to one another to form tke fibre of the sponge. The 
spicules have been clearly demonstrated in several genera, including, besides simple 
forms, the remarkable segmented sponges such as Verticillites, which consist of 
tubular seyments whose walls are formed of close-packed spicules, and which are 
superposed one upon another, the roof of one forming the floor of its successor. 
In the Triassic deposits of St. Cassian in the Tyrol, representatives of the 
Pharetrones occur, in which the fibres of the skeleton are made up, not of spicules, 
but of spheroidal masses, with a radiate structure strikingly resembling the ele- 
ments of the skeleton of Astrosclera.” 
The view of this structure generally held by paleeontologists is that it is second- 
ary, being due to a recrystallisation of the lime. If this is the case, it is certainly 
a remarkable coincidence that the structure should resemble so closely that of a 
living form, which in the larger features of the anatomy of its skeleton resembles 
members of the Pharetrones. A fact which supports the view of the secondary 
nature of the spherulitic structure is that the fossils in which it occurs are the repre- 
sentatives in the St. Cassian beds of both simple (e.g. Corynella gracile, Miinstyr.), 
and segmented (e.g. Enoplocelia and Thawmastocelia) forms of the Pharetrones, 
which as they occur elsewhere exhibit as we have seen well-marked tri- and 
quadriradiate spicules. 
Supposing the spherulitic structure to be secondary in these fossils, the nature 
of the skeletal elements is a definite character dividing Astrosclera from the 
Pharetrones. 
Under these circumstances it seems better to class Astrosclera as the type of a 
new family Astroscleride, possibly allied to the Pharetrones, but certainly without 
close affinity with any other known group of sponges.° 
2. On the Morphology of the Cartilages of the Monotreme Larynx. By 
Jounson Symineton, J/.D., Professor of Anatomy, Queen’s College, 
Belfast. 
This paper contained a description of the cartilaginous framework of the larynx 
of the ornithorhynchus and the echidna, based upon ordinary dissections and 
et hs serial microscopic sections of the organ. 
he condition of the thyroid cartilage in the monotremes is of special interest, 
as it forms the basis of Dubois’ theory of the origin of this cartilage from two 
pairs of visceral arches, the fourth and fifth post-oral. The author referred to the 
different descriptions of this cartilage given by Dubois, Wiedersheim, Walker, 
and Gegenbaur, and showed that it consists of a single piece of cartilage, which 
includes a median ventral part and two pairs of cornua. The median portion is 
not, as usually represented, a separate element or copula, but is directly continuous 
with the cornua, The thyroid cartilage of the monotremes agrees, therefore, with 
that of the higher mammals in consisting of a single cartilaginous mass, but it 
differs in that its anterior and posterior cornua pass from the small median portion, 
or body, round the sides of the larynx in a dorsal and caudal direction nearly 
parallel with one another, and the anterior cornua are further peculiar in being 
eae by a large part of their anterior borders with the posterior cornua of 
e hyoid. j 
_ According to Gegenbaur the cartilage of the epiglottis is a derivative of the 
sixth post-oral visceral arch. He based this theory mainly upon his observations to 
1 These are beautifully shown in the Warminster specimens described by Hinde, 
Ann. and Mag. of Nat. Hist. ser. 5, vol. x. (1882), p. 185. : 
* Cp. Zittel, Grundziiye der Paleontologie, p. 59, fig. 88; also Studien iiber 
ate Spongien, iii., Abh. k. bayer. Ak. Wiss. Cl. ii. Bd. 13 Abth. 2 (1879), pl. xii. 
g. 5. 
5 A fuller and illustrated description will appear in Dr Willey’s Zological Results. 
