IIG CARBONIFEROUS CEPHALOPODA OF IRELAND. 



the shell expands much more rapidly than Phillips's, and cannot be considered 

 identical with it. 



I am not able to agree with de Koninck in regarding the present species as 

 identical with J. de C. Sowerby's species Nautilus globatus { = Planetoceras 

 glohatum, Hyatt, supra ^ p. 96). The distinctive character of that species is the 

 laterally spreading form of the last whorl, with its excessively wide, dorso- 

 ventrally contracted aperture. This expansion of the whorl is always seen 

 commencing in the youug shell, and this in individuals quite as small as the one 

 figured in the plate accompanying tliis description (PI. XXX, fig. 2 a). Besides 

 this, P. globatum has no keels or ridges on the umbilical walls ; it has only the 

 keel on the edge of the umbilicus, very strongly developed in the adult shell. 

 Another feature, absent in Coloceras bisfriale, is very marked in P. glohatum, and 

 that is the last whorl being produced beyond the coiled part of the shell, so that 

 the aperture never touches the penultimate whorl. 



G. histriale is easily distinguished from G. Goyanum by its relatively much 

 larger umbilicus, and by the ridges that encircle the umbilical walls. 



Localities. — Clane, county of Kildare; Tomdeeley, county of Limerick. 



Famihj Solenocheilid^. 

 Genus Aipoceras, Hyatt, 1883. 

 AiPOOERAS OOMPRESSUM, A. H. FoovJ. Plate XXX, figs. 1 a, h. 



1891. GrYEOCERAS (AiPocEEAs) coMPUEssiTM, J. H. Foord. Cat. Foss. Cepli. 



British Museum, pt. 2, p. 68, figs. 6 a, b. 



1893. AipocEHAS COMPRESSUM, A. Hyatt. Carboniferous Cepbalopods. Second 



paper. G-eological Survey o£ Texas, Fourth 

 Annual Eeport, 1892, p. 454. 



Bescription. — Shell compressed, composed of about two volutions which are 

 not in contact ; these increase in diameter with moderate rapidity. The section 

 is roughly trigonal or cuneiform. The initial point is somewhat obtuse ; it bears 

 no trace of a cicatrix. The dorsal area, which is completely exposed, is propor- 

 tionally broad and flattened, and slightly raised along the median line, falling 

 away on either side of this to the subangular umbilical margin. The sides are also 

 flattened, and their junction with the narrowly rounded periphery is undefined. 



The body-chamber is very large, occupying about two-thirds of a volution. 

 There is a slight emargination on the superior border of the aperture, representing 

 the hyponomic sinus. 



