President's Address. 69 



species composing it, of which six are known from the Car- 

 boniferous rocks of Scotland, are turriculated shells. The 

 aperture is oblique, oblong, and produced below, more or less, 

 into the semblance of a very short or truncated canal. A 

 distinct sinus occurs in the outer lip, and a band, single or 

 double, is traceable on all the whorls. Murchisonia, if we 

 omit the tendency to an effuse mouth, stands much in the 

 same relation to Pleitrotomaria that Loxonema does to Macro- 

 cheilus. Professor de Koninck * divided the genus into two 

 sections according to the ornamentation — the M. coronatce, or 

 nodular species, and the M. sulcatce, or striated and grooved 

 forms. The latter section is by far the most numerous, and 

 comprises the whole of the Scotch species. On the other 

 hand the late Mr J. W. Salter selected the form of the whorls 

 with the view of subdividing Murchisonia. He restricted the 

 latter name, unfortunately, to short turbinate shells, and not 

 to elongated and turriculated forms selected by D'Archiac 

 and De Verneuil as the types of their genus. Many of the 

 elongated forms have rounded whorls, and had Salter simply 

 divided the Murchisonise with a lengthened spire, into those 

 with rounded whorls, and those with angular whorls, using 

 his Hormotoma for one of these, it probably would stand the 

 test of investigation. There is, then, no reason why the short 

 turbinate shells, otherwise agreeing with the original diagnosis 

 of Miirchisonia, should not furnish a third section. 



To complete this group of shells we must not neglect to 

 notice Platyschiswta (M^Coy).-)* In this genus are included 

 obtusely conical, ventricose, umbilicated smooth shells, with 

 a shallow sinus in the outer lip, but no defined band. They 

 resemble depressed smooth Pleiirotomarice, devoid of a band, 

 and the sinus reduced to a mere inflection of the outer lip. 

 So far as we know, only one species is met in Scotch Car- 

 boniferous deposits, the Platyschisma ovoidea (Phillips). 



The curious Family of the Capulidae is represented in our 

 Carboniferous rocks by several species referable to the exist- 

 ing genus Cajmlus (Montfort). Several names have been 



* Anim. Foss. Terr. Carb. Belgiqiic, p. 409. 



+ Synop. Carb. Lime. Foss., Ireland, 184-4, p. 38. 



