108 Dr. Henry Hicks — The Age of the Morte Slates. 



in the other fragment of the slate. However, for present purposes, 

 we will take fig. 3 as it stands, and take the objections in the order 

 given by Dr. Gregory : — 



" 1. The hinge-line is recognizable in the specimen shown in fig. 3, 

 although it is not seen in the figure ; the hinge-line is straighter 

 than in the genus StricMandinia, and agrees rather with Orthotetes." 

 This is a photograph and shows all that is to be seen ; what, then, is 

 the meaning of saying that it is not seen in the figure ? I can see 

 it clearly, and I presume others can. Davidson says of S. lirata, 

 "hinge-line nearly straight, and shorter than the width of the shell," 

 and so it is here. Compare also for this purpose figs. 3, 4, 10, and 

 11 on pi. XX, " Silurian Brachiopoda." It is well known that the 

 hinge-line in Orthotetes is usually produced, not rounded at the 

 cardinal extremities. So much for the hinge-line. Next, as to the 

 muscular impressions, we are told " a pair of scars are shown on pi. x, 

 fig. 6, which Dr. Hicks identifies as muscular impressions. If this 

 be correct, it tells strongly against the fossil being a StricMandinia, 

 for the muscular scars are far too large and wide ; they agree with 

 those of Orthotetes, especially with those of the subgenus Hipparionyx." 

 I must once again remind the reader that fig. 6, pi. x is the same 

 fossil as fig. 3, p. 267 ; therefore the size of the scars is to be com- 

 pared with the latter figure, and not with fig. 6 : and w^hat is the 

 result ? The scars reach to less than one-third of the length, and in 

 Davidson's figures (10 and 11) of S. lirata they are exactly one-third 

 of the length. In 0. hipparionyx, on the other hand, as may be 

 seen by examining figs. 8-12 on pi. xvii of Davidson's monograph 

 of Devonian fossils, the scars reach in each case to nearly half of the 

 length of the shell, and in fig. 11 to three-fourths of the length, and 

 in the original figure by Vanuxem they also reach to three-fourths 

 of the length. It is extraordinary that this fact has been so com- 

 pletely overlooked by Dr. Gregory. 



Now as to the width of the scars. As their outer margins are 

 only faintly seen, it is necessary to carry the eye forward from the 

 umbo, which in the cast is raised, and the two pear-shaped scars 

 will then be recognized on each side of the raised poi'tion. They 

 are so much flattened that they can with difficulty be defined from 

 the ovarian spaces which surround them, as is commonly the case 

 in crushed specimens of S. lirata (see especially the type-specimen 

 in the Geological Society's collection, and figured in the " Silurian 

 S^'stem "). The scars, however, occupy less than one-third of 

 the width of the shell, again agreeing fairly with those in fig. 11 on 

 pi. XX of Davidson's monograph. The extraordinary ditierence to 

 this, shown in the original figure of H. proximus, where the scars 

 occupy no less than two-thirds of the width, are strongly raised 

 and joined centrally, and are most strongly defined on their outer 

 margins, will at once strike any observer. These facts are also 

 equally marked in the figures by Davidson of the specimens in the 

 Jermyn Street Museum and elsewhere, obtained from Looe. The 

 shape of the shell also is far more like S. lirata than either Orthotetes 

 or 0. hipparionyx. The other fossils to which he specially refers, viz. 



