{Bumastus trentonensis. 
720 THE PALEONTOLOGY OF MINNESOTA. 
the smaller, now before us, the term Bumastus trentonensis, this process involving 
simply the interchange of the generic names originally applied to the species. 
The original of B. trentonensis was not described, but the wood cuts given of it 
show in both views only eight thoracic segments. There is no evidence from these 
figures that any of the segments have been lost or forced beneath one or the other 
of the extremital shields. 
Mr. Billings’ species Jlle@nus milleri (from various localities in the Trenton 
limestone about Ottawa, and also from the Black River limestone in the township ~ 
of Hull, Canada) is inseparable from B. trentonensis. It was described as having 
nine thoracic segments; Mr. Walcott, however, in identifying J. milleri in the Black 
River and Trenton limestone of New York and the Trenton of Platteville, Wisconsin 
(loc. cit.), suggests that one of the segments of the original was concealed, as his 
specimens showed fen segments. Before me are two entire individuals of this 
species from the Trenton limestone of Trenton Falls; one of them shows ten thoracic 
Fig. 32.—Bumas!us trentonensis Emmons (sp.). An entire individual with ten segments. Trenton 
Falls, New York. : 
segments, the other agrees with Emmons’ original in having but eight. The latter 
has been eroded in such a manner as to afford a complete longitudinal section of the 
specimen, which fully demonstrates that no segment has been lost and that this 
animal at this stage of development possessed no more than eight segments. An 
enrolled individual from the Black River limestone at Poland, N. Y., shows nine of 
these segments. , 
Among the numerous examples of the species which have been received from 
localities in Minnesota and Illinois, enrolled individuals are common, while but a 
Fig. 33.—Bumastus trentonensis Emmons (sp.). An entire but disjointed individual, with nine 
segments. 
single extended example has been observed. This, from the Galena beds at Pleasant 
Grove, Minnesota, has nine segments; coiled specimens from the middle Trenton 
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