G BRITISH DEVONIAN BRACHIOPODA. 



shall endeavour to treat that question in the concluding portion of this monograph, but 

 will, without further observations, proceed with the description of the species we have been 

 able to assemble. 



Family— T EREBRATULID/E. 

 Gen us — Te rebratula, LJh wyd. 



Terebratula sacculus, Martin; variety? PL I, fig. 1 — 8. 



Anomites sacculus, Martin. Petref. Derbesiana, tab. xlvi, figs. 1 and 2, 1809. 



— — Dav. Mori. Carb. Brach., p. 14 and 213, pi. i, figs. 23, 24, 27, 29, 30. 



Terebratula sacculus, Phillips. Palaeozoic Fossils of Cornwall, Devon, and West Somer- 

 set, p. 91, tab. xxxv, fig. 166, 1841. 



— hastata. Ibid., fig. 168. 



— virgo, Ibid., fig. 167. 



— sacculus, A. Roemer. Die Versteinerungen des Harzebirges, pi. xii, fig. 23. 



Specific Character. — Shell ovate, or imperfectly pentagonal, front margin straight, 

 rounded, or slightly emarginated, valves almost equally and evenly convex, with or 

 Avithout a small depression near the front in the central valve, beak slightly produced and 

 truncated by a small circular foramen : beak-ridges more or less defined. Surface 

 smooth. Proportions variable. Two British specimens have measured 



Length 10, width 8, depth 5 lines. 



Observations. — While describing the Terebratula? from the Middle Devonian Limestone 

 of Barton and Lummaton, near Torquay {T.juvenis excepted), Professor Phillips appears to 

 have laboured under the same difficulties and uncertainties I now experience in the 

 identification of these very variable shells. These Barton Terebratulac arc divided by 

 Phillips into three so-termed species ; those that are oblong-ovate with a straight or 

 emarginated front he identifies with T. sacculus ; those that are ovato-lanceolate, uniformly 

 convex, with a prominent beak, and contracted nearly straight front margin, he terms 

 T. virgo ; while others are believed by him to resemble young specimens of T. hastata 

 from the Mountain-limestone. It would not, however, be correct to admit three distinct 

 species out of so variable a shell, and especially so, when in a handful of specimens every 

 gradation of shape can be found connecting the three extreme conditions described by 

 Phillips. At p. 214 of my Carboniferous Monograph, I entered into many details in 



