NEW SPECIES OF CAMBRIAN FOSSILS FROM CAPE BRETON. 
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lobe of the rachis, showing that that lobe is composed of numerous 
somites. 
Size . — The shields of this mutation of A. trisectus attain a length 
of 8 mm. 
Horizon and locality . — In bitumenous limestone bed at McAdam 
shore, Escasonie, Cape Breton. Band, 36, Cambrian. 
A singular condition of preservation of the test of this species is 
the rarity of remains of the thorax Among two dozen heads and 
three dozen tails of this species, only one joint of the thorax was 
observed. 
Larval characters. — The reticulation or furrowing of the cheeks, 
which is so obvious a character of adult head-shields, becomes less and 
less pronounced in the small heads, and disappear in minute ones. 
Faint furrows are impressed at the sides of the main lobe of the 
glabella, opposite the median tubercle, showing a somite here to which 
this tubercle belongs; the examples are 1J mm. long, in which this is 
apparent. 
A pygidium f mm. long shows a comparatively short rachis of two 
segments, of which the anterior is dominated by a low ridge-like 
tubercle ; no true anterior lobe, such as is found in adult shields, can 
be detected at this stage. The posterior lobe, by faint tubercles at 
the sides, is shown to be composed of at least two somites, yet the tri- 
sected condition of the rachis is already apparent. 
Mut. germanus, n. mut. 
This interesting form has many points of resemblance to A. trisectus , 
and is of nearly the same size, but yet is not trisected on the posterior 
lobe of the rachis of the pygidium. This form and mut. ponepunclus 
sometimes occur scattered over the same surface of rock, but more 
frequently are distributed on different surfaces. The smoothness of the 
slopes of the shields and the absence of trisection in the posterior lobe 
might lead one to think it a different species from mut. ponepunctus 
and from A. trisectus , type, but the tubercle at the end of the rachis of 
the pygidium, peculiar so far as the author knows to the Cape Breton 
forms, leads one to think they belong to one species. 
Since writing the above I have received a letter from Prof. J. E 
Marr, of St. John’s College, Cambridge, who has had the examples of 
A. trisectus in the Wood wardian Museum examined, and also those of 
