76 
PATAGONIAN EXPEDITIONS ! PALAEONTOLOGY. 
1873 JValdheimia p. Hutton, Cat. Tert. Moll. Ech. New Zealand, p. 36. 
1885 IV. p. Hutton, in: Quart. Journ. Geol. Soc., v. 41, p. 553. 
1887 Terebratula p. Philippi, Tert. Quart. Verst. Chil., p. 217, pi. 49, f. 
2 (after Sowerby). 
1897 Magellania p. v. Ihering, in: Rev. Mus. Paul, v. 2, p. 267. 
1899 Terebratella p. Lahille, in: Rev. Mus. La Plata, v. 9, p. 289, ff, 
pi. 1, 2. 
Shell oval, more or less elongate, rarely almost as broad as long. 
Both valves nearly equally convex. Beak incurved, with a large foramen ; 
beak ridges blunt. No sinus on the dorsal (smaller) valve. Surface 
smooth, without ribs. 
Measurements'. Length, 59, 40, 30, 25, 34, 31, 27 mm. 
Width, 51, 32, 28, 19, 25, 21, 25 mm. 
Remarks : This species is a Terebratella as has been shown by Lahille, 
who figures the complete brachial apparatus (pi. 1, f. 53, 54, 55). Al- 
though I do not possess any specimens showing this apparatus complete, 
the median septum of many of my specimens shows distinctly a cruciform 
appearance, i. e ., it possesses, near the lower end, processes, which appar- 
ently were connected with the descending part of the loop. The latter, in 
numerous individuals, shows an angular projection just where we are to 
expect this connection, so that there is every reason to believe that a 
bridge extended between the descending branch of the loop and the 
median septum. And further, the close affinity of T. patagonica with the 
following species ( T. gigantea ) — from which it is hardly distinguishable 
specifically — supports this view, the latter being a true Terebratella. 
Lahille has written a separate paper on the variability of this species. 
Although we must appreciate the value of such studies, they never can be 
satisfactory, if the author does not pay due attention to the stratigraphical 
position of the forms in question. I am very much afraid that Lahille in 
his paper confused the present form and the next one; at any rate, I 
doubt very seriously that his statement, that T. patagonica is found asso- 
ciated (p. 5 of separate copy; “dans la meme couche”) with Monophora 
darwini , is correct. The latter species, according to v. Ihering (1899, p. 
42), belongs to the Entrerios formation, which is younger than the Pata- 
gonian, and I am fully prepared to accept this opinion, since among our 
collections from Patagonian beds not a single individual of Monophora is 
found, while T. patagonica is very abundantly represented. If Lahille 
