[ 4i ] 
which is common to all the (hells of the trichitc 
kind [g]. The fpine being formed by protrufion, its 
component parts are adjuffed on a different manner, 
and the pores like thecancelli in bones (though not fo 
diftindt) are irregular, which is thereafon of its break- 
ing obliquely in any diredt ion, but it is generally fmooth 
by being faturated with a plated kind of fpar [/&]. 
My ingenious and very worthy friend Mr. Brander, 
in a differtation on the Belemnite, prefented to the 
Royal Society [z], juftly obfervesj {< that the Be- 
“ lemnite belongs to the teftaceous part of the ani- 
<c mal kingdom, and to the family of the nautili/' 
And I would beg leave farther to add, that this gen- 
tleman’s fentiments are greatly ftrengthened by the 
furprifing analogy, which the Belemnite bears to the 
little pearly concamerated (hell, or cornu Ammonis ; 
and the orthoceratites, to the large nautilus j the 
former having its fiphunculus upon the verge, as 
the latter has it in the center of the diaphragm, or 
partition, of each cell or chamber. “ It has indeed 
been truly matter of fpeculation (continues Mr. 
Brander) how this huge folid fubftance called the 
Belemnite, exclufive of the nucleus, could be formed ; * 
and how it happens, that fome Belemnites fhould have 
the nucleus within them, others not ; the cavity to 
M Fig. 7. A piece of the Penna Marina, perforated by 
the Pholades. 
[b~\ Spar feems to be nothing but cryftal debafed by a cal- 
careous earth : the more debafed fort breaks in a hairy trichite man- 
ner, the more pellucid kind with a fmooth furface; and always in 
an oblique rhomboidal direction; which perhaps may in fome 
meafure enable us to account for its double refraction. 
[fj Philofophical Tranfaitions, Vol. xlviii. for 1754, page 
803. 
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