114 BULIvETiN 5 384 



summit of those segments of the fragment above described, which we 

 have supposed to be second costals, a prominent line on its base corres- 

 ponding with the inner one of those grooves which we have described, to 

 characterize the superior face of those plates. This plate then, agreea- 

 bly to the relations in which we have viewed the preceding pieces, must 

 be a scapula ; it is susceptible of considerable hinge-like motion, and 

 appears to have been much less firmly attached to the costals than the 

 latter are to each other. 



A segment of a crinoid animal, which seems to have been a Jirsi costal 

 joint of a Pentacrinus of Parkinson, occurred near the same place. 



22. Productus pectenoides. Say. Convex valve, with a central longitu- 

 dinal indentation ; the whole surface is longitudinally ribbed, each 

 rib being marked by two striae, in addition to the central carina. 



The shell is not of frequent occurrence, and a perfect specimen has not 

 yet been obtained, but the portions we have examined, are sufficient 

 to show that it is perfectly distinct from either of the species we have 

 mentioned. We do not find any species figured or described by authors, 

 Hke it. 



23. ProducUi,s conipressns. Say. Shell much compressed, with nume- 

 rous, acute striae, upwards of fifty in number on each valve, the alternate 

 ones rather smaller ; a very slight central longitudinal indentation, on the 

 convex valve ; outline suborbicular ; hinge edge rectilinear, shorter than 

 the greatest breadth of the shell. 



Greatest breadth, from 3-5 to i inch. In its proportions it resembles 

 the truncated portion of the productus of Martin, as represented on his 

 plate 22, fig. 3. It is very common. 



24. A shell of the length and breadth of three inches sometimes occurs, 

 the convex valve of which is transversely undulated, its umbo prominent, 

 and curved like that of a Gryphsea, its tip resting on the base of the oppo- 

 site valve, which is concave, with a transverse linear base ; its muscular 

 impressions seem to have been lateral. 



\^Foot note, page 75/] . 



25. A single specimen was found of a valve of a shell, in some degree 

 resembling a pecten, but without the auricles. Length, more than 2 3-10 

 inches. 



26. Productus lineolatns. Say. Valves with numerous, fine, equal, 

 equidistant, longitudinal striae, and a few small tubercles ; convex valve 

 very much elongate, its basal portion is curved downwards, almost per- 

 pendicularly with respect to the disk near the umbones. 



So singular is the structure of this shell, that the internal cavity appears 

 to have been perfectly transverse, with respect to the general length of the 

 shell, and small in comparison with the length. It strongly resembles the 

 Anomites productus of Martin, as represented on plate 22, fig. 102, of his 

 Petrif. Derbi., and like that shell it is armed with small tubercles, though 

 fewer in number, and the strise are much more numerous and smaller. 



27. Cast of a turretted univalve, probably a Cerithium, of the length of 

 21-2 inches. 



28. Cast of the anterior portion of a valve of a shell like an Ostrea, of 

 the breadth of 21-2 inches. 



29. On the Missouri near the Platte, occur masses of rock, which seem 

 to be almost exclusively composed of a remarkable petrifaction, belonging 

 to the family of concamerated shells. This shell is elongated, fusiform, 

 and when broken transversely, it exhibits the appearance of numerous 



[Long's Expedition to the Rocky Mountains, Vol. I, 1823]. 



