GENERA OF THE SUBORDER PENTAMEROIDEA 



177 



Genus ZDIMIR Barrande 1881 



B.irrande, Syst. Sil. Centre Bohcmc, vol. 6, 1881, p. 171, 

 pi. 292, figs. 1 7-20. 



Genoholotype. — Z. solus Barrande. 



Discussion. — A single isolated valve from the De- 

 vonian of Bohemia, of "unusual and enigmatic" ap- 

 pearance, was named Z/iimir and provisionally referred 

 by Barrande to the Pelecypoda. The specimen, ac- 

 cording to the author, resembles the arched valve of 

 certain elongate pentamerids, but is slightly inequi- 

 lateral. He states further that the specimen has a 

 moderately developed, curved beak, almost as in the 

 pentamerids, without trace of an area, and the surface 

 of the beak is broadly open. The exterior is orna- 

 mented by cost.T diverging from the beak. No muscle 

 or pallial marks were observed. Aside from the allu- 

 sions to its possible affinities with the pentamerids, 

 Barrande compares the specimen with Isocardia and 

 places it in the Pelecypoda. 



It was later referred to as scarcely separable from 

 Uncites gryfhus by Freeh.** Novak,'* however, 

 studied and prepared a specimen of Z. solus in the 

 Bohemian museum at Prague, showing that fragments 

 of the shell substance adhering to it had the structure 

 of brachiopod shells and that it had a spondylium sup- 

 ported by a septum. Ztlimir is therefore quite clearly 

 a pentamerid. In 1913 Schuchert"" considered the 

 genus as a synonym of C onchidium . The latter genus 

 is, however, not certainly known in the Devonian. 



Barrande has described many species of Gyp'tdula 

 from Bohemia but Novak claims that Zdimir is not 

 referable to any of them. Two courses can be taken 

 with this doubtfully valid genus: (1) the name can be 

 restricted to the existing specimens; or (2) it can be 

 placed provisionally as a synonym of Conchidium 

 which is known doubtfully from the Devonian. 



C apeUinirllit Strand 

 Holorliyncluts Kiaer 

 Harpidium Kirk 



Costa tse 



Rhifid'tunt Schuchcrt and Cooper 

 Conchidium Linna;us 

 Brooksina Kirk 

 Platymerella Foerste 

 Cymbidiuni Kirk 

 Virgiana Twenhofel 



The genetic relationships are thought to be as shown 

 in Table 20. 



Discussion. — The Pentamerinx are a large and 

 interesting group of shells intimately tied together by 

 their rather elongate and non-galeate form as com- 

 pared with the Gypidulina. Internally their spon- 

 dylium is like that of the other subfamily. In the 

 dorsal interior the only difference of note lies in the 

 septa, which are less bowed than in the Gypidulinas. 



The subfamily is provisionally divided into two 

 groups on the basis of its external sculpture. The 

 significance of this division is discussed in the pre- 

 liminary remarks. Suffice it to say here, that nearly 

 every smooth stock is represented by an equivalent 

 costate one. For example, Pentamerus represents a 

 flattish smooth stage, and has its costate equivalent in 

 Rhifidium. 



The writers found that Orthotropia, which has 

 long been classified with the Pentamerina;, is actually 

 an orthid. In the ventral valve it has a pseudospon- 

 dylium and in the dorsal there is a short cruralium 

 occupied by a prominent, simple cardinal process. The 

 structure of Orthotropia allies the genus with Lino- 

 porella, but its exterior is at present unknown. 



Subfamily PENTAMERINX Waagen 1883 



Large, rostrate, elongate, non-galeate Pentam- 

 eridas, usually without distinct interareas. It is in this 

 subfamily that the internal characters of the family 

 are t)'pically developed. Shells smooth, costate or 

 multicostate. 



Geologic range. — Silurian and early Devonian. 



Has the following genera: 



Laeves 



Pentamerus Sowerby 



Pentameroides Schuchert and Cooper 



Lissocceitna Schuchert and Cooper 



" Zeits. deut. geol. Gesell., vol. 38, 1886, p. 920. 

 '» Ibid., vol. 40, pp. 588-590, 1888. 

 ^^ Zittel-Eastman Text-book of Paleontology, 2d ed., vol. 

 l,p. 394. 



Laves or Smooth Pentamerinse 



Genus PENTAMERUS Sowerby 1812 



PL 27, figs. 4, 8, 9, 10, 12, 15, 17-19; pi. 29, fig. 11; 

 t. fig. 26 



Sowerby, J., Min. Conch., vol. 1, 1812, p. 73, pi. 28. 

 Davidson, Brit. Foss. Brach., vol. 1, Introd., 1851-1855, 



p. 97; vol. 3, pt. 7, 1866-1871, pi. 18, figs. 1-12, 



pi. 19, figs. 1, 2 {oblongus). 

 HaU and Clarke, Pal. N. Y., vol. 8, pt. 2, 1895, p. 236, 



pi. 67, figs. 11-13, 20, pi. 68, figs. 1-8, pi. 69, 



figs. 1-14, pi. 70, figs. 1-5, t. figs. 169-171 (all of 



oblongus) . 

 Syn. Pentaiicre Blainville 1824, Diet. Nat. Sci., vol. 32, 



p. 301. 



Genolectotvpe (Hall and Clarke). — P. Itpvis 

 Sowerby 1812. 



Description. Exterior. — Shell large, pentagonal- 

 hexagonal in outline, commonly trilobate in front; 



