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[Assembly 
Detthyres. 
Ddthyris bilobata. — Shell small, ventricose, profoundly bilobed; sur- 
face with radiating striae. Locality j same as the preceding. 
Third Group. 
Crustacea. 
Platynotus. — Depressed, apparently not contractile. 
Buckler^ with oculiferous tubercles, situated on the front or middle 
lobe. Abdomen with about 12 articulations; mesial and lateral lobes de- 
pressed; ribs with oblique grooves. 
Platynotus Boltoni. — Syn. — Paradoxides Boltoni, Bigsby. It is un- 
necessary at present to give a minute description of this species; 
but I will remark, that the peculiar situation of the eyes in this trilobite 
removes it from any genus hitherto established; in which opinion I am 
confirmed by that of my friend. Professor Green. There is a splendid 
specimen of this species in the collection of the Albany Institute, depo- 
sited by Judge Buel. 
Fifth Group. 
Pterinea. 
1. Pterinea pholadis. — Shell profoundly elongated, ventricose; dor- 
sal and basal margins parallel; posterior side rugose, or with short un- 
dulations near the dorsal margin. Length, II inches. 
2. P. modiolaris. — Shell ovate oblong, compressed; surface with 
coarse concentric lines, obsolete on the posterior side; posterior ex- 
tremity obliquely truncated. Length, nearly 3 inches. Locality, Pu- 
laski, Oswego county, with the preceding. 
Cyrtolites. 
Shell with the general form of CyrtoceraSj but destitute of septa. 
Cyrtolites ornatus. — Shell with transverse rounded ribs and fine striae; 
periphery acutely carinated. Length, 1 inch. Locality j Washington- 
ville, Oswego county. 
Sixth Group. 
Trocholites. 
Shell in the form of an Ammonite; volutions contiguous, gradually 
increasing in diameter; septa plain. 
