TRILOBITRS. 7a7 
Harpina ottawensls.] 
thoracic segments in the former, investigated the nature of the hypostoma of both 
and found therein differences so notable that he introduced the name Harpina for 
the early Silurian species; a term which we retain as probably applicable to all our 
American forms. 
Formation and locality—From the middle portion of the Galena limestone, Hader, Minnesota. 
Collector, Mr. BE. O. Ulrich. 
Harpina, cf. H. orrawensis Billings (sp.). 
Among the material obtained from Dr. Robbins is a large horseshoe-shaped 
impression of the exterior of the submarginal doublure of the head-shield. It is 
quite flat and its ornament apparently consisted of a great number of fine punctze 
of about equal size except along the inner margin where they are larger and 
confluent in radial lines, forming a series of short divergent furrows. The marginal 
Fig. 79.—Harpina, cf. H. ottawensis Billiugs. 
outline of the shield is quite similar to that of H. ottawensis Billings,* of the Trenton 
limestone of the city of Ottawa. Indeed, the specimen conforms almost exactly in 
size and curvature with the original figure of that species. We have above observed 
that species with a concave cephalon may have a perfectly flat doublure, and I am 
disposed to believe that this specimen probably represents an individual of H. 
ottawensis, with which it presents an additional point of agreement in the character 
of the surface puncte. 
Formation and locality——Galena limestone, Wykoff, Minnesota. 
HARPINA RUTRELLUM, %. Sp. 
An hitherto undescribed species is represented by a head-shield with the 
following characters: Size moderately small, outline subsemicircular. Surface 
convex, somewhat depressed above; marginal border not so broad as in H. minneso- 
tensis; deeply concave. Margin thickened, smooth and slightly upturned. Genal 
extremities not retained. Glabella subconical, extending more than one-half the 
*Palzozoic Fossils, vol. i, p. 182, fig. 165, 1865. 
