TEANSACTIONS OF SECTION C. 635 



vault were continued down the sides of the ambulacral grooves, which could thua 

 be closed in completely and converted into tunnels, as in recent Crinoids. 



The classification of the Blastoidea must depend entirely upon morphological 

 principles. Mere differences in the relative sizes of the calyx plates are of very 

 little systematic value; and difierences in the numbers of side plates on given 

 lengths of the ambulacra are absolutely worthless. On the other hand, the 

 structure and relative positions of the hydrospires and spiracles are morphological 

 characters of much svstematic value. 



5. On the Characters of the ' Lansdown Encrimfe' (Millencrinus Prattii, 

 Gray, sp.) Sij P. Herbekt Caepenter, M.A. 



The 'Lansdown Encrinite ' is a species of MiUericrimis (M. Prattii, Gray, sp. = 

 Apiocrinns ohconicits, Goldfuss) from the Great Oolite on the top of Lansdown, near 

 Bath. It is remarkable for the very great variation in the characters of its stem 

 and calyx. The former may reach 50 mm. in length, and consist of 70 discoidal 

 joints; or there may be less than 10 joints, the lowest of which is rounded off 

 below, and its central canal closed up. Various intermediate conditions may occur 

 between these two extremes, while in some specimens there may be only 2 to 4 

 stem-joints ; and in one case the whole stem is represented by a slightlv convex 

 imperforate plate on which the basals rest. This specimen, taken by itself, would 

 be naturally regarded as a Comatula of advanced age, in which the cirrhus-sockets 

 had disappeared from the centro-dorsal just as they do in the recent Actino7netra 

 Juki'sii. The general appearance of the calyx is very similar to that of Pentacrinus 

 Wynllc-TJiomsoni ivnm the North Atlantic. But it is remarkable for the number 

 of small intercalated pieces which it may contain. The basals are frequently 

 separated from one another, or from the radials, by minute plates which, while 

 regularly developed all round the calyx in some specimens, are entirely absent in 

 others. 



Tlie nearest allies of J/. Prattn seem to be M. Munsferianus, var. Buchianus, 

 and M. Kodotianus. It stands on the extreme limit of the genus, connecting it 

 with Pentacrinus on the one hand, and with the free Comatulidce on the other. 

 It is thus a synthetic type, as would naturally be expected from its geological 

 position ; for it is probably the earliest known species of the genus, except 

 perhaps for two doubtful Liassic forms, which are known only by isolated plates 

 and stem-joints. 



6. On the Lov;er Keuper Sandstone of CJicshire. Bij A. Stkahan, M.A., ' 

 F.G.8., Geological Survey of England and Wales. 



This paper deals with some of the results of the re-survey of parts of Cheshire, 

 which have been already described in detail in the Geological Survey Memoirs 

 'On the Neighbourhood of Prescot' (.3rd edition), and 'On the Neighbourhood 

 of Chester.' Several sections, of which the best are at Euncorn and Frodsham, 

 show that there is a strong and constant division between the Waterstones and 

 the Keuper Basement Beds. These were formerly classed together under the 

 name of Lower Keuper Sandstone, but, so far as the re-survey has been carried, 

 are now distinguished on the maps. The old and new classifications may be 

 compared as follows : — • 



Okl Classification New Classification 



Keuper Marl Keuper Marl 



( . . , "Waterstones 



Lower Keuper Sandstone ■ . . , Lower Keuper Sandstone or 



I Basement Beds 



The Basement Beds, which form bold escarpments, consist of courses of hard 

 building-stone with partings of soft sand, and a considerable thickness of soft 

 current-bedded sand at top, distinguished by the name of the Frodsham Beds. 



