Great Oolite near Basle, 51 



small size of its constituents. The Gastropods are rarely 

 more than 1 centimetre in length, and Terebratala maxlUaia 

 averages 3 millimetres. These fossils are trae dwarfs, not 

 merely young forms ; the stunting of growth is accompanied 

 by no other change of character. It is, however, noticeable 

 that the dwarfs are confined to the lenticular fossil masses ; 

 the same species when found, as a few of them are, in tiie 

 freestone courses are of normal size. S >me species are con- 

 fined to the freestone and are never found as dwarfs. 



The difficulty of figuring these minute fossils was overcome 

 by M. Greppin in an ingenious manner, which he was good 

 enough to explain to me. A fossil was fixed between wire 

 points in the field of a microscope and its shadow thrown by 

 a strong light on to a piece of ground glass. On this the 

 outline was traced by a pencil. The object was then ex- 

 amined by refiected light in the usual way, and the details 

 filled in on the glass ; any error can be rectified in a moment 

 on this sm-face. When the glass was filled with drawings it 

 was photographed and phototype plates then made. This 

 method combines accuracy, clearness, and softness, with the 

 great advantage of the author being his own artist. 



The Crinoid stem-fragments, to which I would now direct 

 attention, are found by hundreds at both Muttenz and Buben- 

 dorf, and are often slightly worn. Tliey share the stunted 

 character of the other fossils, and appear to be the dwarf 

 varieties of two species. 



Of these species one is already known as Pentacriaas 

 Nicoleti, Desor. The greatest diameter of the stem in the 

 present specimens (5 millim.) is, however, less than the 

 smallest diameter yet recorded for P. Nicoleti^ and the 

 majority of tlie fragments have a diameter of only 3 or 4 

 millimetres. I have therefore suggested that tiiey should be 

 known as P. Nicoleti^ var. ininimus (fig. 1, p. 52). Examples 

 of this variety, found in the Great Oolite of NeueWelt byMons. 

 J. B. Greppin, were seen by me last year in the Strassburg 

 Museum (Elsass-Lothringen Sarnmlung). The fragments of 

 this species are distinguished by the re-entrant angle of the 

 lateral faces, and by the depression of the sutures at the angles, 

 from the other fra2:ments fuund in the lenticular beds of 



o 



Muttenz. 



Of what species this other Pentacrinus is the dwarf I do 

 not know. I can find nothing exactly like it among Jurassic 

 species, and this, combined with its small size, has induced me to 

 designate it Pentacrinus Basileoi (from Basilea^ Basle) (fig. 2). 



4* 



