296 Miscellaneous. 
Measurements of the Trunk of the Aurochs. 
Inches. 
Length of vertebral column from the atlas to the sixth caudal 
vertebra, measured across the diapophyses .......... 81 
Length of vertebral column over the neural spines ...... 88 
Length of cervical region over the diapophyses.......... 17 
Length of dorsal region GULEO | he Eset ns es eats 6 ree 
Mength of lumbar resion),;, (ditto e-e2 fe welsh taieve ge = Peace 13 
Length of sacral and six caudal ditto ................ 21 
Wepth of spine of seventh, ceryieal fas. '5) eee else ae 8 
Depth of spine of first, second and third dorsal, being the 
three longest, (Cneh a aii). cies. ou sine attee = otal ae 11 
eng th Ol frst TID yo. bl) cheysies: bis 1s ee ee eee ey eee 9 
Length of ninth, or the longest 22.6 Saree snc eee 183 
Seven ribs articulate by separate hemapophyses to the sternum. 
Length of diapophysis of fourth lumbar, or the longest .. 43 
Breadth of atlas across the neural arch................ 7 
Extreme breadth across the spines of the ilia  .......... 14 
Extreme breadth across the pubis, from the inner edge of 
eacmacetaDUlum jc, «o's es ya wine hata coco isleteieto Wee ean 
MISCELLANEOUS. 
On the Velvet-like Periostraca of Trigona. By J. E. Gray, Esq. 
In my account of the species of the genus Trigona of Megerle, I 
mentioned that several species were covered with a velvet-like 
silvery coat hiding the surface of the horny periostraca. 
When this coat is minutely examined, it is found to be formed of 
numerous elongated spicula of a uniform length placed side by side 
perpendicular to the surface of the periostraca, so as to form a pile 
like velvet or plush. The length of the spicula, and consequently 
the thickness of the coat, increases towards the margin of the shell. 
This coat is generally rubbed off from the more convex part of the 
specimens which have not been very carefully preserved, but in such 
examples it is usually to be found near the edge of the valves, or on 
the lunule and other sunken portions of the surface. 
The Rey. Dr. Fleming has lately drawn my attention to the fact, 
that these spicula are siliceous and similar to those of siliceous 
sponges ; indeed Dr. Fleming is inclined to regard the velvet-like coat 
as a species of Halichondria parasitic on the shell rather than as a 
portion of the periostraca itself; and Dr. George Johnson of Ber- 
wick, who examined Dr. Fleming’s specimen with me, is inclined to 
take the same view of the question. 
With these authorities opposed to my view I have reconsidered 
the question, but I am still inclined to believe that I am correct in 
considering the spicula as part of the shell formed by the animal as 
it produces the periostraca on the edge of the shell, and offer the 
following reasons in support of this conclusion :— 
Ist. This kind of coat is found on several species of the genus 
which inhabit different parts of the world. 
