AKT. 32 A NEW PENTAMEROID BRACHIOPOD KIKK 3 



mens 'are relatively narrower and less deep, as indicated by the 

 following measurements : 



Length 4.0 cm. 



Maximum breadth 3.2 cm. 



Maximum depth 2.9± cm. 



It is to be noted that the disproportion between the size of the valves 

 becomes more marked with age, in the adult specimen the pedicle 

 valve greatly exceeding the brachial valve in size. 



The pedicle valve is narrow in its apical portion, highly arched, 

 and with a strongly incurved beak. Anteriorly it remains highly 

 arched, but gradually a flattened median area is developed that 

 changes to a broad, well-defined sinus. The cardinal slopes are long 

 and 'are as sharply defined as in Conchidium^ other than as not being 

 differentiated by being smooth as opposed to the plicated remainder 

 of the shell. The delthyrium is large and bordered on either side 

 by a well-developed heavy convex deltidial plat. When the del- 

 tidial i^lates are not present their former lines of attachment can 

 be seen as narrow, sharply incised grooves at the margins of the 

 delthyrium. The brachial valve is highly arched in the younger 

 specimens, becoming relatively less so with increasing age. The 

 apical portion is strongly incurved. As in the pedicle valve the 

 brachial valve develops a broad median sinus. The surface of the 

 shell is marked by fairly strong growth lines. The shell substance 

 is fibrous, with the fibers running longitudinally. When partially 

 exfoliated, under a magnifjdng glass the fine longitudinal fibrous 

 structure can occasionally be seen. 



The septum of the pedicle valve is very short, but deep. It is 

 concave at the anterior wall. The spondylium, supported only in 

 its posterior portion, is a great sickle or scimitar-shaped affair, in 

 proportion to the septum, being much larger than in any other knov/n 

 pentameroid. The septa of the bracliial valve lie subparallel or 

 slightly divergent, are low, and support the normal crural structures 

 for Conchidhun. 



Horizon and locality. — From the limestone of the Brooksina hori- 

 zon on the north shore of Heceta Island and the south shore of Kos- 

 ciusko Island, Southeastern Alaska. 



C otypes. —C'At. Nos. 70'2'28, 70220, U.S.N.M. 



IIARPIDIUM ROTUNDUS, new species 



PkUe 2, fig. S 



At a somewhat higher horizon than the main horizon of 77. iri- 

 simm occuivs another Ilarpidium that seems to l>e distinct and for 

 which the name Harpidium rotimduH is here proposed. 



As known H. rotundvs is a smaller species than 77. indf/nis. tiie 

 largest undoubted representati\e of the species giving the following 



