THE AEENIG AND LLANDEILO EOCKS OF ST. DAYID's. 659 



nearly three tenths of an inch ; and its width slightly exceeds three 

 tenths. Two of its contiguous series of hydrothecse only are shown ; 

 aud at their line of junction they appear to have split slightly apart, 

 exposing a slender rod, on either side of which there is a free space, 

 apparently indicating that the walls of the thecse did not extend 

 quite to the centre of the organism. This seems to prove the presence 

 of a virgula in the genus Phylhgraptus, and that its hydrothecse, in 

 each series, freely communicate with one another. No evidence of 

 such a structure, however, has been detected in the specimens of this 

 geuus from the Quebec Group ; nor has such been furnished by the 

 more imperfectly preserved specimens from the Skiddaw Slates. 

 Loc. Lower Arenig, Road Uchaf, Ramsey Island. 



Section Retioloidea, Lapworth. 



Family GLOSSOGRAPTID.E, Lapworth. 



Genus Glossogeapttjs, Emmons. 



Glossogeapttjs ciltattjs, Emmons. PI. XXXIV. figs. 7 a & 7 b. 



1855. Glossograjptus ciliatus, Emmons, American Geology, vol. i. 

 p. 108. pi. i. fig. 25. 



Subfusiform, with broadly rounded extremities, about one inch in 

 length, and having a maximum diameter of one eighth of an 

 inch ; virgula and lateral spurs invisible ; hydrothecae 25 to the 

 inch ; apertural spines placed perpendicularly to the line of the 

 ventral margin at their point of origin, stout, slightly arcuate, 

 and about one tenth of an inch in length. 



The fragment figured, which is the only specimen of this species 

 obtained from the St. -David's beds, has almost exactly the same 

 number of hydrothecEe to the inch as are found in the typical example 

 given by Dr. Emmons. Only a single row of apertural spines is 

 apparent on each margin ; and the two longitudinal series of lateral 

 processes, characteristic of this genus and its very intimate ally 

 Retiograptus of Professor Hall, are wholly invisible. The great 

 rigidity and extraordinary length of the apertural spines form the 

 chief peculiarity of this species. Emmons's figure shows exactly the 

 same relative development of these appendages. They are, however, 

 figured as being slightly narrower and less rigid than they are in 

 our example, while the polypary itself is proportionally broader. 



Loc. Upper Arenig, Llanvirn Quarry. 



Family GLADIOGRAPTID^E, Lapworth. 

 Genus Teigonogeaptus, Nicholson. 

 Teigonogeapttts ensieoemis, Hall, sp. PL XXXIV. figs. Scir-Sc. 



1851. Oraptoliihus ensiformis, Hall, Rep. Geol. Surv. Canada for 

 1850, p. 133. 



