APPENDIX. 5 



Palaeontologists therefore appear in general to agree, as to the propriety of placing in a separate 

 group such organisations as T. concentrica on the one hand and T. Herculea on the other, but differ 

 considerably as to the names to be adopted for each in particular. I am quite disposed to relinquish the 

 proposition made in pp. 85 and 88. The matter may stand thus : 



Page 87. 



Athyris, M'Coy, = (or) Spirigera, V Orbigny, for such shells as A. concentrica, A. lamellosa, 

 A. pectinifera, A, Roissyi, &c. ] 



Page 84. 



For " Athyris" = read " Sub-genus — Merista, Suess," for T. Herculea, T. tumida, T. scalprum, 

 T. cassidea (Dal., sp.), &c, and 



Page 88. 

 Sub-genus — Retzia, King, for T. Adrieni, T.ferita, T. serpentina. 



Page 89. 

 Genus— (Incites, Be/. 2 



1 The arrangement of the crural processes, attachment, and direction of the first spiral coils in this, 

 and in other species of the genus, Athyris, M'Coy = Spirigera, D'Orb., has not as yet been completely 

 understood, nor have the many efforts made in that direction both by Mr. S. P. Woodward and myself 

 been attended with results which may be termed entirely satisfactory. 



In the 'Manual of the Mollusca,' Mr. S. P. Woodward has represented what he supposes to be the 

 probable arrangement, and states (p. 224), " hinge plate with four muscular cavities, perforated by a small 

 round foramen, and supporting a small complicated loop (?) between the spires ; spires directed outwards, 

 crura united by a prominent oral loop. The foramen in the hinge plate occupies the situation of the notch, 

 through which the intestine passes in Rhynchonella." I cannot, however, at present, entirely coincide in 

 the opinion expressed by my able and conscientious friend, not from any positive observations to the con- 

 trary, but because I am rather inclined to believe, that only one attachment took place from the base of the 

 hinge plate (as in Spirifer), forming at the same time the spire and complicated crural process; or in other 

 words, that the loop (?) described by Mr. Woodward is not independent of the crura and spiral appendages. 

 I would therefore urge upon those naturalists who may possess specimens of A. Roissyi in a favorable 

 condition for observation (as they do often occur near Tournay), to endeavour to clear up this unsettled, 

 and important character of internal organisation. 



2 In p. 90, I quoted as examples, JJncites Gryphus, Schloth., and U.lcevis, M'Coy; the last reference 

 was given upon Professor M'Coy's authority, but I do not feel quite certain that U. Icevis belongs 

 to the genus, and according to Mr. Salter it would be the same as Ter. porrecta, Sow., 'Min. Con.,' 

 tab. 5/6, fig. 1, which I believe to be a Stringocephalus. I also unintentionally omitted to observe in 

 p. 89, that Professor M'Coy's views on this genus differ entirely from those advocated in the present 

 volume ; thus in p. 380 of the 'British Palaeozoic Fossils' (1852), the genus Uncites forms alone the 



" Vlth Family — Uncittdje of Professor M'Coy. 



" Genus — Uncites (Defrance), as here defined. 



"Gen. Char. Shell elongate-ovate, slightly inequilateral ; substance very thick, densely fibrous ; beak 

 of the receiving valve very long, narrow, claw-shaped, gently incurved obliquely on one side ; ivith a wide 

 concave imperforate defined channel beneath, no internal septa, nor appendages in either valve." 



Professor M'Coy also states, " having first ascertained the true internal characters of that curious 



