ANIMALS. 125 



elusion, I have seen punctures in species of every genus of Spiriferida, so that I am led 

 to conclude a punctated structure characterised the entire family,^ The only difference 

 prevailing as regards the punctures, is in their size : in Trigonotreta Walcotti they are 

 large ; in T. undulata they are extremely small ; and in Spirifer heterodytus they are 

 intermediate in size. 



The proximate affinities of Spiriferida have not as yet been satisfactorily determined ; 

 their spiral labial appendages associate them with Hypothyridce ; but to which genus 

 of this family they are immediately related, is far from being sufficiently clear. 

 Isorhynchus, concluding from the form of some of its species, offers the nearest 

 approach to certain Silurian Trigonotretas, notably the T. Marklini [Spirifer, id.) of 

 De Verneuil. 



Spiriferida were very abundant during the primary period ; but at its close, 

 particularly in the Permian division, they appear to have decreased considerably as 

 regards numerical amount of species, though not in the same respect in genera ; 

 since four or more groups of this kind, viz., Trigonotreta, Cleiothyris, Martinia, and 

 probably Spirifer^ were then in existence. During the secondary period only two 

 genera, represented by the Trias Trigonotreta fragilis, including the Jurassic species, 

 and a Martinia (vide postea) are known to have been living. 



Our next step will be to notice the various genera included in the present family 

 as given in the Synoptical Table. 



Genus .Spirifer, J. Sowerby, 1815 (= Cyrtia, Dalman, 1827). 



This genus is typified by the Anomites cuspidatus of Martin — a remarkably inequi- 

 valved shell ; with an elevated area ; an upright pedicleiferous umbone ; and having, 

 according to M. Deshayes, the fissure closed in all its extent with a deltidium furnished 

 towards its apex with an oval-shaped foramen.^ 



^ The punctures are best seen by candle-light, with a Stanhope lens. In looking for punctures, 

 Trigonotreta Walcotti should be examined first : in the split laminae of this species the punctures are seen 

 intersecting the capillary fibres, both of which are large compared with what they are in those species in 

 which they are generally considered to be absent. 



2 From the description which Count Keyserling gives of his Spirifer SchrenJci (vide Raise in das Petchora- 

 Land, p. 234) found in the Permian limestone of Petchora, I am disposed to conclude that it is a true 

 Spirifer. 



3 " Posee sur sa valve superieure cette coquUle a la forme d'une pyramide triangulaire dont la plus 

 grande surface, la seule qui soit plane, est formee par le crochet tout-a-fait droit de la grande valve ; cette 

 surface est traversee dans toute sa hauteur par una goutti^re triangulaire ; si la mati^re dure de la couche 

 qui la remplit ordinairement a ete enlevee, on trouve cette goutti^re ferm^e dans presque toute son etendue, 

 at offrant, vers le sommet, un trou ovalaire, de sorta que cette coquQle, malgre I'etrangete de sa forme, a en 

 effet las caract^res des T^rebratules." (Animaux sans Vertebras, 2"* Ed., vol. vii, p. 368, 1836.) 



