32 Mr. T. Davidson on Recent Terebratulge. 



who admits both Terebratella and Megerlia, must, I fear, have 

 overlooked the fact that T. sanguinea, Chemnitz, possesses a trebly 

 attached loop as in Megerlia, since he places it in Terebratella, 

 and allows T. truncata to remain with Megerlia. It is evident 

 to me that either T. sanguinea will require to be classed with 

 Megerlia, or King's subgenus should be rejected and located 

 among the synonyms of Terebratella* ; but from this, in my 

 present opinion, no advantage would be gained. We must proceed 

 further, if such is to be our plan ; for it is highly probable that 

 we should be obliged to include Kraussia among the modifica- 

 tions of Terebratella, and dispense with the subgenus, were we 

 to allow such shells as T. sanguinea and T. truncata to be located 

 in two different genera. I well remember how puzzled my 

 friend Woodward and myself were, in 1851 and 1852, while 

 studying several species and specimens of Kraussia ; for we found 

 that the apophysis in some of the species and specimens became 

 at times branched, and indicated a decided tendency to attain 

 the form of Megerlia ! I can hardly credit, therefore, that all 

 these modifications or intermediate conditions can claim the 

 rank of independent genera, or, rather, to be of equal value 

 with other genera, such as Spirifer, Orthis, &c. ; but by allow- 

 ing them the title of subgenera of Terebratella, we are at once 

 enabled to keep closely grouped what should not be separate in 

 our classification of the species f. 



Before passing to other matters, let us cast a glance at another 

 example. Terebratula proper, exemplified by T.vitrea, possesses 

 a small, simple, unreflected loop, composed of two short riband- 

 shaped lamellae attached to the hinge-plate, and united in front 

 by a transverse lamella bent upwards in the middle. This cha- 

 racter is constant in two or three recent and in several fossil 

 species ; but in Terebratulinu the loop is also similar to that of 

 Terebratula in the young age, becoming annular in the adult by 

 the union of the crural processes. It seems to me, therefore, 

 that this last is a mere modification of Terebratula, not deserving 



* In 1852, while working at my 'Sketch,' I had not made out the fact 

 (for which we are indebted to Mr. Reeve) that T. pulchella, Sow,, was a 

 synonym of T. sanguinea, Chemnitz. At the period just mentioned I had 

 not been able to examine a complete specimen of what I considered to 

 represent T. sanguinea (enough of the septum remaining only to mislead 

 me into the belief that it belonged to Terebratella), but, from finding the 

 triple attachment in T. pulchella, I placed it with Megerlia, where I am now 

 disposed to leave T. sanguinea. 



t A great deal is still to be found out relative to the development of the 

 loop by an attentive examination of shells in their various stages of growth ; 

 and the reader is referred to a paper by Mr. C. Moore, in the December 

 number of 'The Geologist' for 1860, where certain modifications in the 

 loop of the fossil Terebratella Buckmani have been described and illustrated. 



