CLASSIFICATION OF THE BRACHIOPODA. 125 



genus Spondylohus^ seems to me very doubtful, and although far removed by the author 

 from Crania, and placed among the Lingulidce, would appear to be more nearly related 

 to Retzius's genus. 



Professor M'Coy states that in Spondylohus the larger valve is " slightly longer, from 

 the apex being perfectly marginal and slightly produced, channelled by a narrow groove 

 below, the anterior end of which is flanked by two very prominent, thick, conical shelly 

 bosses, representing hinge teeth!' In Crania Hagenovii (De Kon.) there are two similar 

 bosses,^ which did not perform the office of hinge teeth, but were probably points of attach- 

 ment for one of the sliding muscles. 



Numerous and varied forms of Crania have been described and illustrated by 

 several authors, and in particular by Hceninghaus^ and Goldfuss,* who published beautiful 

 monographs of the species of the genus known to them. 



Geol. range. — Crania is one of the oldest types of animal life, it first appeared in the 

 lower SUurian period, and has lived throughout all subsequent periods up to the present 

 time. 



Examples : C. Brattenburgensis, Stoboeus, sp. ; Ignabergensis^ Retzius ; abnormis, 

 Def. ; costata, Sow. ; antiqua, Def. ; spinulosa. Nils. ; antiquior, Jelley ; Moorei, Dav. ; 

 Parisiensis, Def, ; tubercidata, Nils. ; ringens, Hcenig. ; rostrata, gracilis, armata, inter- 

 media, bipartita, of Munster ; obsoleta, Goldfuss ; Cenomaniensis, D'Orb. ; anomala, 

 MiiUerj Hagenovii, De Kon., &c. 



Family— DISCINID^. 



Animal attached by the means of a muscular peduncle, passing through the ventral 

 or lower valve, a slit in the hinder portion, or a circular foramen excavated in the substance 

 of the same valve. Arms fleshy ; valves unarticulated. 



In this family we have two or three genera, viz., Discina, Trematis, and Sipho?iotreta. 

 The genus or sub-genus Trematis, as well as the sections Orbiculoidea and Acrotreta, will 

 require further investigation before being definitely admitted. 



' The species named as types, are C. Sedgwiekii, Lewis, and craniolaris, M'Coy. 

 ^ My attention was called to this point by my friend Mr. Woodward. 

 ' Beitrage zur Monog. der-Gattung Crania, 1828. 

 * Petrefacta Musei Universalis, 1840. 



^ This species was named after lynaberg, a small village in Scania ; Stoboeus, Retzius, and others have 

 spelt it Egnab, an error I likewise committed in Part II, p. 11. 



