512 Notices of Memoirs — On Silurian LeperditicB. 



proaching Primitia mundula in its bituberculate furrow. We will 

 name this variety tuherosa. 



All these specimens of B. impendens are rather more oblong than 

 those met with in the Pentland Hills ; and the three lobes of the 

 valve are not so distinct. Length of valve, -j-L-th ; breadth, -g-'^th inch. 



3. Primitia^ protenta, sp. nov. [Fig. 3.] — One cast is decidedly 

 referable to an elongate-oblong, convex valve, with a centro-dorsal 

 furrow and a pair of small distinct symmetrical tubercles, one on 

 each side of it, along the middle line of the valve. 



This is longer than B. impendens and its variety above mentioned, 

 and more symmetrical ; for it must have been almost cylindrical in 

 the perfect state of united valves ; and its two tubercles are lower 

 down, further apart, sharper, and more equal than in JB. impendens, 

 var. tuherosa. Length of valve, -j\th ; beadth, -^'-oth inch. 



4. Entomis acicidata, Jones, 1871, MS. Annals Nat. Hist. 1873, 

 ser. 4, vol. xi. p. 416 ; Monthly Microscop. Journ.^ 1873, vol. x. p. 

 76. [Figs. 4a. 4&.] 



Several casts indicate a small Entomis related to E. impendens, 

 Haswell (" On the Silurian Formation in the Pentland Hills," 1865, 

 p. 38, pi. 3, fig. 11), but narrower and more pointed in front, and 

 bearing a subcentral pointed tubercle, or spine (well-marked on 

 some external moulds of the valve), low down, and in front of the 

 long transverse furrow, which is characteristic of the genus. Length 

 of the valve, y-^-th ; breadth, gL-th inch. 



I. — On the Silurian LEPEKciTiiE of Eussia, etc. By Magister 

 Fe. Schmidt. [Miscellanea Silurica. I. Ueber die russischen 

 silurischen Leperditien, mit Hinzuziehung einiger Arten aus dem 

 Nachbarliindern. Von Mag. Fr. Schmidt, Mem. I'Acad. Imp. des 

 Sciences de St. Petersbourg, vii. serie, vol. xxi. no. 2. 1873.] 



IN this monograph of the LeperditicB of Eussia and the neighbour- 

 ing countries, M. Fr. Schmidt has revised the known Leperditice 

 and IsochilincB, and has added several new species. He figures and 

 describes three Isochilince : — I. Biensis (Grunewald), I. j^unctata 

 (d'Eichwald), and /. MaaMi, nov. sp. ; and ten Leperditice : — 

 L. grandis (Schrenck), L. Barbotana, sp. n., L. Tyraica, sp. n., L. 

 Angelini, sp. n., L. BaUhica (Hisinger), L. Hisingeri, sp. n., L. Eicli- 

 waldi, sp. n., L. Wiluiensis, sp. n., L. parallela, sp. n., L. marginata 

 (Keyserling), L. Keyserlingi, sp. n. 



IsocMUna punctata and some Primitice, but no true Leperditice, 

 have been yielded by the Lower Silurians of Eussia. In the 

 lower zones of the Upper Silurian, characterized by the smooth 

 forms of Pentamerus (zones 4, 5, and 6 of the Esthonian series), 

 Leperditice abound ; Z. Hisingeri occurring in all. In Gothland 



^ " JBeyrichia," by inadvertence, in the former description. 



^ In the memoirs here referred to, " the Pentland Hills " are given by mistake, 

 instead of Peeblesshire, as the locality. 



