OSTEAOODA. 683 



Moorea? perplexa.] 



MOOREA ? PERPLEXA, W. Sp. 



PLATE XLVI. FIGS. 17 and 18. 



Size.— Length 0.85 mm.; hight 0.62 mm.. 



The figures present such a remarkable valve that I am quite unable to account 

 for its peculiarities. Unfortunately the original of the drawings, which were made 

 four years ago, has been mislaid or lost, so that I am obliged to publish them without 

 a final verification of the characters shown. It may really be a Moorea, but I doubt 

 it. Or it may be related to Placentula. With more material its affinities may become 

 clear, and it is the hope that collectors will search for and perhaps succeed in 

 rediscovering the species, that has induced me to retain it in my report. 



Formation and locality.— MiAdlei third (Rhioidictya bed) of the TrentoQ shales, near Fountain, 

 Minnesota. 



Genus Maceonotella, n. gen. 



Carapace convex, semicircular or semiovate, with a long, ncdrly straight, hinge; 

 valves equal, full centro-dorsally, without ridges or a sulcus, but exhibiting a smooth 

 subcentral spot where the ornament is omitted; surface, in the only species known, 

 coarsely punctate. 



Type: M. scofieldi, n. sp. 



I saw no way to escape the responsibility of erecting a new genus for the fol- 

 lowing species without forcing it into one of several that I am fully persuaded ought 

 not to receive it. The long hinge, semicircular outline, and almost perfectly equal 

 ends, rendering it difficult to distinguish one from the other, give it an expression 

 peculiarly its own. Kirkbya permiana Jones, it is true, has a somewhat similar form, 

 but like all the species of that genus, it has also a marginal ridge and a subcentral 

 pit, neither of which are present in the species under consideration. Still, the 

 smooth spot mentioned above probably represents the pit of Kirkbya, and it is with 

 this genus that I think the affinities of Macronotella lie rather than with either 

 Aparchites or Isochilina. The Isochilwa rectangularis Ulrich (Jour. Cin. Soc. Nat. 

 Hist., vol. 13, p. 182; 1890) from the Devonian at the falls of the Ohio, may be 

 congeneric with M. scofieldi, there being some similarity in their outlines, but as 

 the surface of the Devonian form is perfectly smooth and not inflated centro- 

 dorsally, I hesitate to say it is. 



