2 APPENDIX. 



distinct pallial line." ('Manual of the Mollusca,' p. 279, 1854.) Refer also to a very able memoir by the 

 same author, read to the Geological Society, on the 7th June, and published in the ' Quarterly Journal' for 

 the present year. 



Page 73, line 6. 



Add — M. E. Deslongchamps has published in the ' Annuaire de l'lnstitut des Provinces,' for 1853 

 and 1854, descriptions and figures of three remarkable shells or species, discovered by himself and Dr. 

 Perier, in the Middle and Upper Lias of May, Fontaine-Etoupefour, and Bretteville-sur-Laize, near Caen, 

 by the names of Argiope Perieri, A. Liasiana, and A. Suessii ; thus carrying the genus Argiope to the 

 lower portion of the Jurassic system. I will not offer any positive opinion on this question until 

 I have had an opportunity of examining the species in question ; but about the period of my friend's 

 publication in 1853, I could not refrain from expressing certain objections or doubts, based upon the 

 character of their plication, which differs so entirely from that of any other species of Argiope at present 

 known. The external shape, of one of them in particular, A. Liasiana, has much of the external shape of 

 certain forms of Cyrtia, especially by its deltidium and position of the foramen ? It will therefore be 

 necessary to know more of their internal arrangements, before the place of those remarkable species can be 

 definitely established. 



Page 77, Thecidium. 



The valuable and beautifully illustrated memoir ' On the Brachial Arrangement in Thecidium,' by 

 M. Suess, of Vienna,' has afforded us much additional knowledge relative to the internal structure of this 

 remarkable genus ; and my only regret is not being able to transcribe the whole of that very important 

 memoir, which does infinite credit to the persevering and able researches of its distinguished author. 



M. Suess begins by stating, that the near connection between Argiope and Thecidium has already 

 been admitted by several authors, but he forcibly objects to those two genera being considered Brachiopoda 

 cirrhid.e, and combined with the Rudista, as proposed by M. A. d'Orbigny; the animal having proved 

 that they are not only true Brachiopoda, but likewise members of the great Family TerebratuliDjE. He 

 also believes that Stringocephalus must be connected, or placed in the same family and close to Argiope ; 

 he has observed on the inner edge of the loop of the last, small lamellar projections, similar, although 

 much less developed than in the first-named genus. M. Suess then enters into many interesting details 

 on the variations presented by the loop of Argiope : of which Arg. decemcostata and A. decollata have 

 afforded the greatest difference. The first approaches most to that of Stringocephalus, the second 

 teaches us to understand the more complicated structure in Thecidium. 



It has been already shown, that the exterior side of the loop of A. decollata is at times partially fixed 

 to the bottom of the valve, while the outer margin bears the brachial fringe. Now if we imagine the 

 inferior side to be fixed to the valve and to the septa all the way round, we should have the counterpart of 

 appareil ascendant 2 of Thecidum digitatum ; and the appareil descendant would be wholly wanting in every 

 genus of Brachiopod known to M. Suess. Many authors, he states, may be deceived, while thinking that 

 the broad wide expansions of the appareil descendant could be formed, by the union of the portion of the 



1 ' Proceedings of the Imperial Academy of Sciences of Vienna,' vol. xi, pp. 991 and following, 1S53. 



2 The words appareil ascendant, appareil descendant, bride transversale, &c, as used by M. E. 

 Deslongchamps, have been explained in pp. 78 and 79 of the ' Introduction.' The ascending apparatus of 

 Thecidium appeared to Mr. S. P. Woodward and myself to be nothing more than the equivalent of the 

 "septum" of Terebratella, Magas, Argiope, &c. ; the cirrated lip commences on the outer edge of the oral 

 processes and is continued along the outer edge of the loop. 



