114 Jlie America?i Geologist. February, i89u 
Cambrian series with the determination that the series is Pre- 
Cambrian.* 
Middle Cambrian. The Cambrian of America has been 
least studied in the Middle or Paradoxides zone, mainly owing; 
to the relative paucity of the strata of that age, but, neverthe- 
less, much has been done in places; for example, the St. John's 
group has been carefully studied by Matthew in New Bruns- 
wick. It is, then, important that each new bit of evidence bt- 
carefully garnered and studied. In accordance with this plan 
I began the study of the locality of Braintree a few years ago. 
carrying on the work as opportunity served. It is a promis- 
ing locality for extensive and systematic work and it will 
doubtless yet give us a large fauna. The fauna, as is known 
at present, is as follows: Trilobita, — Paradoxides harlaiii 
Green; Agraidos quadrangularis Whitfield; Ptychoparia rogersi 
Walcott: Pteropoda,— //I't'/^y^'j- shalcri Walcott, and H. hay- 
i^>ardic/isis Grabau. To these I have to add a brachiopod, 
Obolella gamagei, n. sp. 
OBOLELLA GAMAGEI, n. sp. 
Description. Dorsal valve (?). General shape, elliptical or sub- 
circular, appearing slightly wider on the left side of the longitudinal 
axis, owing to distortion. Surface relatively smooth, two well marked 
concentric lines of growth being present, also some obscure radial 
plications, best shown on the left side of the longitudinal axis; the 
position and obscurity of these strias mark the species as being a 
relatively smooth shell type. The beak is less prominent on the whole 
than in the nearest related types, Obolella crassa Hall and O. atlantica 
Walcott, being very similar. Probably the internal shape was not ma- 
terially different. The beak of the specimen was detached when the 
slab was split apart, adhering to the opposite side, when this was 
cleaned away, the form was found to be as indicated by the dotted 
*The writer wishes to direct attention to the work of 'Wv. John Sears, 
of Salem, Mass., as being in a region (Essex county) on the line of 
strike of the formations found in this area, Middlesex county. Mr. 
Sears has made discoveries of fossils in limestone similar to that de- 
scribed by the writer, but the limestone of Essex county is described 
as the remnants of a superficial sheet belonging to the Cambrian off 
the coast. ^ The researches of the writer result in the conclusion that 
the limestone of Lincoln can only be older than the Cambrian, being 
interbedded in the Lincoln slate. The existence of worms or even of 
Hyolites does not prove a Cambrian age. We have a vast time before 
the Cambrian out of which the highly differentiated Cambrian faunas 
came. The persistence of the type Lingula is a warning against the 
localization of genera in time and space. There is nothing to show 
that Hyolites had not a hoary past at the beginning of the Cambrian. 
