•106 DR. GW\N JEFFREYS ON MOLLTJSCA OF THE L'^P r • ' ^> 



and other seas. The septum in the very young of T. cranium consists 

 of a mere upright point, as in Megerlia ; and the loop is then round 

 and small, becoming elliptical and extended in the adult. The 

 foramen is incomplete in the young of T. septata, and resembles 

 that of T. cranium in every state ; and this is likewise the case as to 

 the young of T. vitrea. 



Mr. Dall, in the 'American Naturalist' for March 18/1 (vol. v. 

 p. 55), indicated a new genus of Brachiopods, founded on some 

 young specimens of T. cranium which I had sent him from the 

 'Porcupine' dredgingsin 1869. He said the loop " has no secondary 

 attachment to the haemal valve, and the latter is destitute of a 

 septum." This genua he proposed to name Frenula, and the 

 species Jeffrey sii. In the American Journal of Conchology for 1871 

 (vol. vii. pt. 2, p. 65, pi. ii. figs. 7-10) he gave a more detailed 

 account, with figures, of the same species as Ismenial jeffreysi. 

 His figures agree with those published by Herr Friele to illustrate 

 the development of the skeleton in T. cranium. Mr. Dall remarks 

 as to his species, " Without a septum in either valve. Loop un- 

 attached except by the haemal processes to the hinge plate," and 

 further on, " None of the specimens had the slightest trace of a 

 septum." He then alludes to having subsequently received from me 

 other young Brachiopods, of which he says, "All of them possessed 

 a filiform but rather stout septum ; " and, although with some 

 doubt, he was of opinion that all the specimens belonged to the same 

 species, and that in those first mentioned " the septum must have 

 been broken away." He has since, at my request, kindly sent me 

 for my inspection a specimen of his species, which he now calls 

 Megerlia jeffreysi, and which he says he received from me as the 

 young of T. cranium ; and he has presented me with some valves 

 dredged by him at Port Etches in Alaska, at a depth of about 15 

 fathoms, and which according to him were "probably" the same 

 species, although he carefully explained that he would not vouch 

 for it. The valves in question were worn and apparently old, but 

 all of them showed the septum most distinctly ; and they may 

 belong to the species which Mr. Dall has very lately described anew 

 as Megerlia jeffreysi. These valves are not unlike Terebratella (?) 

 frontalis of Middendorff in shape and texture ; but they differ 

 essentially in the position of the septum as well as in the deltidium. 

 In Mr. Dall's imperfect specimens the septum resembles that of 

 Terebratella spitsbergensis, viz. in being a long narrow and thread- 

 like lamina extending from the middle of the deltidium for about 

 two thirds of the inside towards the front ; in T. frontalis (judging 

 from the type most obligingly sent me by Dr. v. Schrenck from the 

 St. Petersburg Museum for my inspection) the septum is that of 

 Argiope, being gnomon-shaped or triangular, and placed near the 

 front. The apophysis of Megerlia truncata does not correspond 

 with that of any of the above-named species. I would here remark 

 that the septum is not at all likely to be broken away and entirely 

 disappear, because it is formed in the protected part of the lower 

 valve. It is persistent in the most worn and even fragmentary sp*e- 



