340 R. B. Nenion — On Tremafonohis. 



length of ventral aspect of volution z=z 35 mm. ; wiJtli of ventral 

 aspect of volution i= ISmm. ; width of the lip = 15 mm. 



Ohservations. — The most perfect of the two specimens shows 

 hoth surfaces but dorsally the expansion is obliterated by matrix. 

 The perforations, though perhaps not quite so regularly placed as 

 observed in Hall's drawing of the type species, are nevertheless 

 prominent and unmistakeable. They are somewhat obscure on the 

 ventral face of the whorl, where probably they are more or less 

 filled up ; but slight risings and depi'essions in the central ridge 

 seem to indicate their presence. Viewed dorsally this character is 

 more striking. Here the holes are narrow and elongate, the central 

 one being longest; they are raised and quite distinct, with a depres- 

 sion between each. After extending to within about three-fifths the 

 length of the shell the perforations cease and the central ridge 

 becomes more or less merged in the longitudinal striee which 

 ornament the fossil. Adherent to the surfaces of this specimen 

 are some imbedded examples of Spirorbis Lewisi [tenuis),^ and some 

 Polyzoon growths. The second specimen is a cast of the dorsal 

 surface only, in which the siphonal openings are present but fewer, 

 thus forming a distinction which might be a reasonable excuse for 

 treating it as a separate species but in the absence of additional 

 material it is perhaps safest to regard it as the same. The expansion 

 is absent but the radiating striae observed near the spiral region 

 are sufficient to indicate its existence when the shell was more 

 ■perfect. The margins in both specimens are quite entire, there being 

 no evidence of an apertural sinus. The umbilical areas have suffered 

 through pressure and are consequently obscured, so that their exact 

 limits cannot be accurately appreciated. 



This new species bears a resemblance to BeUerophon dilatn{us^ of 

 J. de C. Sowerby, from the Ludlow rocks of Burrington ; but that 

 shell is more largely umbilicated and its central ridge is non- 

 perforate. An unfortunate mistake regarding this species was made 

 by Mr. S. P. Woodward, who figured on plate xiv. fig. 28 of his 

 celebrated "Manual of the Mollusca " the B. clilatatus and named it 

 BeUerophon expansus, a shell which has a deeply sinuate margin 

 and is altogether quite distinct from the more robust form of the 

 other species which has its margin entire. 



This error has been copied by Dr. Paul Fischer, who, using the 

 same plates for his "Manuel" as illustrated Woodward's earlier 

 work, suggests a relationship between B. expansus and Trematonotus, 

 the B. dilatntus being clearly the form meant in his reference. After 

 an examination of several specimens of this species, both at the 

 Geological Museum, Jermyn Street, and at the British Museum, no 

 trace of perforations could be discovered. The Wenlock specimens 

 differ also from the type T. Chicagoensis, which has a wide umbilicus 

 exposing all the spiral system, though in the elongate character of 

 its dorsal orifices it appears to be remarkabl}' similar. 



An analogy, at first sight, seems to exist between the British 



1 Murchison's Silurian System, 1839, pi. 8, tig. 1, pp. 616, 617. 

 - Murchisou's Silurian System, 1839, pi. xii. ligs. 'Z'6, 24, p. 627. 



