Structure and Classification of the Asterolepidse. 501 



does not belong to Pterichthjs after all, but is an unmistak- 

 able Bothriolepis, closely allied to B. canadensis. This is at 

 once apparent from the restored figure of its upper surface 

 which I have given on PI. XVIII. fig. 4. It differs some- 

 what in the sculpture of the plates, which is delicately pitted- 

 reticulate, while in B. canadensis it retains rather more of a 

 confluent tubercular character over most parts of the cara- 

 pace. The proximal joint of the arm seems also slightly 

 longer in proportion to the distal, and the denticulation of 

 its outer margin rather coarser. 



It is quite obvious that, as Hugh Miller and Sir P. Eger- 

 ton have already pointed out (8, pp. 311 and 314), Homo- 

 thorax Flerningii, Ag. (4, tab. xxxi. fig. 6), is founded on a 

 bad drawing of the under surface of the species under con- 

 sideration. 



B. major, Ag. sp. { = Pterichthys major, -^g- 5 Placothorax 

 paradoxus, Ag.). — This has been already referred to Bothrio- 

 lepis by Lahusen (11), whose opinion I can amply corrobo- 

 rate. Its remains, as they occur at Scat Craig, near Elgin, 

 are very fragmentary ; but I think they are identifiable with 

 those which occur at Heads of Ayr in a more perfect state. 

 Tubercles of the surface confluent, sometimes into tortuous 

 ridges, more generally forming a reticulation, the stellation of 

 their bases often observable ; limbs with the proximal joint 

 proportionally long and slender. 



B. macrocephalus, Egert. sp. [ = Pterichthys macrocephalus, 

 Egert.). — The long arms and the shape of the anterior parts 

 of the ventro-lateral plates clearly show that this minute 

 species is a Bothriolepis and very closely allied to B. hydro- 

 philus, Ag. sp. This is quite evident from a glance at Sir 

 Philip Egerton's figures (9) ; but I have also carefully 

 examined the type specimens in the British Museum. The 

 body-plates are sculptured with a delicate reticulate pitting 

 also resembling that of B. hydrophilus. 



In the ' Geological Magazine ' for last month (November) 

 I have named and briefly defined two additional species, 

 viz. B.' giganteus, Traq., from the Upper Old Red of Alves, 

 near Elgin, and B. obesus, Traq., from a similar horizon 

 near Jedburgh. 



MiCROBRACHius, Traquair, 1888. 



(=iPteriehthys, pars, C. W. Peach; Microhraehius, Traq., Geol. Mag. 



Nov. 1888.) 



The small species discovered by the late Mr. C. W. Peach 

 in the Lower Old Eed of John o' Groats, and named by 



