CONOCARDIUM FUSIFORME. 467 



Dimeiisions. — PL LIT, fig. 1, the type figured by M'Coy as Pleurorhynchus 

 fuslformis, measures — 



Antero-posteriorly .... 130 mm. 

 Dorso-ventrally . . . .95 mm. 



From side to side . . . .82 mm. 



Shell somewhat crushed. 



Localities. — Ireland : the Carboniferous Limestone of Malahide, co. Dublin ; 

 Hook Head, co. Wexford ; Bushy Island, co. Limerick. 



Observations. — The type specimen figured by M'Coy is fortunately preserved in 

 the Griffith Collection in the Museum of Science and Art, Dublin, and I am per- 

 mitted to refigure it by the kindness of the authorities. It is a very fine and large 

 example, with the right valve somewhat crushed into the left, but the latter 

 retains the outer coating of shell. This species occurs in large numbers in a bed 

 of limestone on the foreshore at Malahide, co. Dublin. Sections of these have 

 been worn down by wave action, but they are so intimately attached to the matrix 

 that it is almost impossible to extract specimens. 



G. fusiforme is distinguished at once from G. EonincJd by the want of a marked 

 constriction between the body of the valve and the anterior wing; but it seems to 

 me very probable that the G. Herculeam, de Koninck (PI. LI, figs. 10 and 11), is only 

 a less fully grown example of M'Coy's species. De Koninck writes of his species, 

 "II offre beaucoup plus de ressemblance avec le G. fusiforme, F. M'Coy, auquel je 

 I'ai assimile pendant quelque temps, mais qui s'en distingue par le faible 

 developpement de la grande concavite de sa lunule cordiforme, ainsi que par la 

 longueur et la foi-me cylindrique de son rostre." 



It is certain that none of the figured specimens of G. Herculeum have so con- 

 cave a posterior surface as the picture of this portion of the shell given by M'Coy ; 

 but this Avas very largely idealistic, for the type is crushed and not well developed 

 in this position. I possess a specimen of the Belgian shell which has a very con- 

 cave posterior surface, which shows that the concavity depends on the extent of 

 the growth of the outer margin of the posterior surface, corresponding to the 

 flange of G. Hibernicum. With regard to the question of the extent and shape of 

 the rostrum, de Koninck describes this process as being broad, terminating in a 

 point, and never prolonged as a cylindrical tube. This maybe the case, or it may 

 well be that specimens have never been obtained w^hich had such a fragile and 

 brittle portion preserved. Little or nothing, on the other hand, is known of the 

 condition of the rostrum in G. fusiforme ; I have seen no specimens in which it is 

 preserved. The base of this process is only preserved in M'Coy's specimen, PI. 

 LII, fig. 1, but in his description he mentions it as "the slender conical tube." 

 The young and intermediate stages of the growth of G. fusiforme are quite 

 unknown, and, curiously enough, all the specimens at Malahide seem to have 

 arrived at mature growth. 



