FISHES OF THE CARBONIFEROUS SYSTEM. - 903 
HARpACANTHUS FIMBRIATUS, Stock., sp. 
Plate XXI, Figs. 11, 11%. 
I have recently received from Hon. William McAdams, of Alton, Tl. 
a small spine which is represented by the figure (11) now given. It was 
taken from the Saint Louis beds of the Lower Carboniferous limestone near 
Alton. It is imperfect, but as it is new to our fauna, and is apparently 
identical with a spine recently described from the Lower Carboniferous 
limestone of Scotland, I have considered it worthy of notice. 
Two specimens only of the species have been known hitherto; they 
were both found at Gilmerton, near Edinburgh, Scotland. The first was 
described by Mr. Thomas Stock in a paper ‘On the Structure and Affinities 
of Tristychius,”' and was referred to that genus with the name Tristychius 
fimbriatus. The second specimen was found at the same locality three years 
later, and was made the subject of a paper on “Harpacanthus, a new genus 
of Carboniferous Selachian Spines,” by Dr. R. H. Traquair, F. R.S.* From 
a study of the second specimen found, which was more complete than the 
first, Dr. Traquair showed that it could not be included in Tristychius, 
which has a compressed and striated shaft with two rows of denticles on the 
posterior margin, while the spine described by Mr. Stock has a smooth and 
polished surface, a circular section below, and a single row of relatively 
large denticles set along the posterior margin near the summit. He there- 
fore made it the type of a new genus, which he called, from its curved out- 
line, Harpacanthus, or sickle spine. ‘The base is recurved and terminates in 
an expanded and club-shaped extremity ; the entire length is about two 
inches. 
Our specimen lacks both base and summit, and yet it reproduces the pe- 
culiarities of the central portion of the Scotch specimens so exactly, that Iam 
compelled to regard it as specifically identical with them. Where fractured 
below our spine is cylindrical, has a smooth and polished surface, with a 
central cavity which reaches nearly to the summit. The upper portion 
seems to have been somewhat compressed and the sides excavated in a broad 
shallow furrow. 
1 Annals and Magazine of Natural History (5) XII, pp. 177-190, pl. 7. 
2 Annals and Magazine of Natural History for December, 1886, 
