170 



GENERA OF THE SUBORDERS ORTHOIDEA AND PENTAMEROIDEA 



middle of the space between the septal plates is a low 

 ridge with diductor scars on each side which probably 

 served as a cardinal process. The adductor impres- 

 sions are four in number, a posterior pair located on 

 the outside of the anterior ends of the septal plates, 

 and a larger anterior pair that is elongate or sub- 

 trigonal in outline. 



Geologic range. — Middle Silurian to Lower 

 Devonian. 



American Species 



Anastrofhia brevirostris (Hall) 1852 

 A. internascens Hall 1879 

 A.interflicata CHiW) 1852 

 A.verneuili (Hall) 1857 



European Species 



Anastrofhia deflexa {Siov/erhy) 1839 

 A.magnifica Kozlowski 1927 



Distinguishing characters. — Anastrofhia is dis- 

 tinguished from Parastrophinella chiefly by the more 

 completely costate exterior. 



Discussion. — ^There is some variation in the spon- 

 dylium of Anastrofhia. In some specimens it is sup- 

 ported for its whole length by the ventral septal plates, 

 but in others the posterior end rests on the floor of the 

 valve. In one unique individual (pi. 25, fig. 42) the 

 walls of the spondylium have bent inward and united, 

 forming a tubular chamber open at the front and back. 

 Such a structure must have impaired the activity of the 

 muscles and is regarded as a pathologic case. In many 

 of the specimens the scar of the pedicle attachment is 

 to be seen in a depression on each side of the spon- 

 dylium just beneath the tooth ridges. The ventral 

 beak and the dorsal umbo as well are commonly more 

 or less abraded by the pedicle. 



The cardinalia of the dorsal valve are typical of the 

 family. There are long brachial supports and outside 

 of these are broad, alate expansions. The posterior 

 ends of the septal plates unite with the inner surfaces 

 of the alae, which are carinate, thickened in the back, 

 and slope off on the outside to unite with a thick, 

 concave plate that serves as a socket. Adductor scars 

 are visible at the front ends of the septal plates, not 

 having become enclosed as in the Pentamerinae. 



several longitudinal plications chiefly developed towards 

 front end; beak high, incurved, with open delthyrium; 

 small false area on each side; interior with small subum- 

 bonal spondylium and short median septum. Brachial valve 

 with lower beak than opposite valve; low median fold near 

 anterior end, composed of several longitudinal plications; 

 interior with pair of long recurved crura, pair of long 

 parallel median septa, and muscle-scars as in Parmtrofhia. 

 Shell thick, fibrous, punctate externally. 



Discussion. — In the absence of material. Reed's 

 genus is difficult to place in our taxonomic scheme. 

 From the morphology as described by him, it is evident 

 that Metacamerella is very close to Parastrophinella 

 and to Anastrofhia. It differs from the former extern- 

 ally in possessing a fold on both valves. Unfortunately 

 Reed's illustrations do not adequately bear out this 

 statement, as figure 18, of the dorsal valve, shows a 

 decided sulcus and appears to be a totally different shell 

 from the one under consideration. Figures 15 and 17, 

 however, clearly have a fold. According to Reed, the 

 muscle marks of the dorsal valve are like those of 

 Camerella (Parastrofhia), but the figures again, except 

 for figure 18, do not show them. Should figures 14 

 and 18 represent opposite valves, the genus would not 

 be difficult to place and we could say at once that it is 

 structurally a Parastrophinella with fold and sulcus 

 reversed, and clearly belongs in association with Ana- 

 strofhia and Camerella. 



The question of punctation among pentamerids is a 

 very important one. Reed states that the punctation 

 is external, and we have shown in our discussion of 

 orthids that exopunctse have no taxonomic significance 

 beyond genera. This is best seen in Porambonites and 

 Linoforella, genera that have developed the same kind 

 of exterior, but the former has an impunctate shell 

 and the latter is endopunctate as in the Dalmanellacea. 

 From the internal characters of Metacamerella it 

 would appear to be impunctate as are all other 

 pentamerids. 



From the above discussion it seems best to place 

 Metacamerella close to Anastrofhia, the chief known 

 generic difference of the former being a fold on the 

 ventral valve. Were it not for Reed's assertion that 

 Metacamerella possessed a dorsal fold, which seems 

 unlikely, to judge by the ventral valve he figures, we 

 would exclude from his genus his figures 15 and 17. 



Genus METACAMERELLA Reed 1917 



Reed, Trans. Roy. Soc. Edinburgh, vol. 51, art. 4, 191 7, 

 p. 934, pi. 23, figs. 14-18. 



Genoholotype. — Stricklandia ? balcletchiensis 

 {balclatchiensis) Davidson 1883, Brit. Foss. Brach., 

 vol. 5, Sil. Suppl., p. 166, pi. 9, figs. 27-29. 



Original description. — Shell oval, biconvex. Pedicle- 

 valve with low median fold near anterior end composed of 



Family PENTAMERIDS McCoy 1844, 

 emend. 



Terminal, usually rostrate Pentameracea, probably 

 derived out of the Camerellids. Shells smooth, costate 

 or multicostate. Ventral interareas short and narrow, 

 but often obsolete, or plane areas are developed. In 

 nearly all there is a more or less large spondylium 



