24 J. W. Jackson—Brachiopod Morphology. 
are given by Beecher’ as belonging to the same genus, viz. Mihlfeldtia, 
but this is incorrect, as dental plates are entirely wanting in the 
former and are well- developed i in the latter. é 
A. truncata was made the type of Megerlia by King in 1850,’ but 
this name being preoccupied by a genus of Diptera in 1830, Bayle, 
in 1880,° established the genus Mauhlfeldtia for its reception. 
Dall, in 1870,* placed sanguinea in the genus /smenia, King, but as 
this genus was founded by King on Terebratula pectuneulordes, Schl., > 
Dall, in 1895,° proposed Frenulina for the A. sanguinea, Chem. 
Points of difference in the early stages of loop development, 
together with the presence of dental plates in one and their absence 
in another, seem good ground for the separation of these two, forms 
into different sub-families, Mihlfeldtia truncata being placed in the 
Magellanine and Frenulina sanguinea remaining in the Dallinine. 
The adoption of this course would necessitate the changing of the 
term Mihlfeldtiform stage in the Dallinine to Frenuliniform stage. 
One remarkable point of difference in the development of the loop 
in I. truncata is clearly seen in the figure given by Fischer & Oehlert* 
of an early stage of this species. Here the loop is strikingly like the 
early stage of Tvrebratella dorsata, figured by Beecher.* There appears 
to be no stage like this in the Dallinine, where the descending 
branches of the loop appear early and are connected, thus forming 
a complete primary loop, whereas a feature of the Magellanine is the 
development of a secondary loop in the middle of the valve on the top 
of the septum, before the appearance of the primary lamelle. 
Deslongchamps’ figure ® of a young example of H. truncata, 2mm. in 
length, also shows a condition of loop somewhat similar to that of an 
adult Uegerlina lamarckiana (another member of the Magellaninz) 
figured by Beecher.” Some difference, however, is presented by the 
former having the ascending branches united to form a ring, whereas 
in 1. lamarckiana the ring is incomplete.” 
The loop of Frenulina sanguinea, on the other hand, passes through 
early stages exactly like those of Macandrevia cranium. 
RHYNCHONELLIDS. 
In describing the manner in which the delthyrium of Hemithyris 
becomes partially closed, Thomson ” calls attention to a curious plate 
on the inner side of the apex of the pedicle valve. This plate, a kind 
of continuation of the deltidial plates, is free in front and separated 
from the shell by a narrow cavity. This feature, which I have 
termed the ‘‘pedicle collar’? in my forthcoming report on the 
1 “* Revision,’’ etc., pp. 383-4. 
* Mon. Perm. Foss. England (Pal. Soc.). 
Journ. de Conchyl., xxviii, p. 240, 1880. 
Amer. Journ. Coneh., vi, p. 129, 1870. 
Not 7. pectunculus, Schl. ; see King, op. cit., p. 245. 
Op. cit., p. 724. 
Op. cit., pl. vii, fig. 1lw. 
Op. cit., pl. i, fig. Da. 
Copied by Davidson, op. cit., p. 106, fig. 9. 
10 Op. cit., pl. i, fig. Db. 
11 See also Davidson, op. cit., pl. xxi, fig. 11. 
12 Op. cit., p. 390. 
ao ty Ona fF 
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