HARDWICKE'S SCIENCE-GOSSIP. 



37 



seems to indicate that the deposit is of ancient origin, 

 and this is further confirmed by the appearance of 

 the Diatoms ; although no new genus has been ob- 

 served, and not more than three or four new species. 

 Many of the forms have an old world look, and 

 exhibit minute differences from those of more recent 

 times. 



As this deposit will perhaps become better known, 

 and, as before observed, access to Herr Grunow's 

 original paper is somewhat difficult, I propose giving 

 a list of the new species and varieties, and figures of 

 three of the most remarkable. 



Cymbella abtiormis, var. antiqua, Grun. ; C. 

 austriaca, var. prisca, Grun., var. excisa, Grun. ; 

 C. gastroides, var. neogena, var. dubrdvka, var. c?-assa, 

 C. lanceolata, var. cormita ; C. sturii, Grun. 



S. intermedia, Grun. ; S. brevistriata, var. subacute, 

 Grun. 



Surirella dementis, Grun. Valve linear-lanceolate, 

 gradually constricted towards the apices, slightly 

 cuneate ; aire almost obsolete ; canaliculi marginal 

 9 in. "ooi"; centre of valve with a slightly elevated 

 ridge or median line not reaching the apices, and 

 terminating in short and sometimes curved spines. 

 Length of valve, •0040 to '0x348; greatest breadth, 

 •0012" to •0015" '; breadth at centre, •ooo6"to 'oooS". 



This very remarkable form approaches in general 

 appearance very near to the genus Cymatopleura, 

 but a careful examination shows that its proper 

 position is in with the Surirella;. The inflations so 

 conspicuous on the frustular view of the species of 

 the former genus are absent, and in their place alas 



Fig. 40. — Epithemia cistula, ""- 



Fig. 41. — Staurosira Harrisonii, 

 var. atnphitetras. 



Epithemia cistula (Eh.) var. hinaris, Grun. Valve 

 arcuate, ventral margin slightly rounded opposite the 

 turgid dorsum ; ends produced slightly inflated : 

 costae distant ; irregular striae moniliform. Length, 

 •0020 to •0030. 



Herr Grunow considers this form to be a var. 

 of Ennotia cistula (Eh.). I have examined Ehren- 

 berg's figures of this species (of which there are 

 several in the " Microgeologie "), but cannot see 

 any resemblance between them and the above-named 

 variety. 



Navicula nobilis (Eh.) Kg., var. neogena, Grun. ; 

 N. viridis, Kg., var. semicrnciata, Grun. ; N. 

 impress7is, var. semicrnciata, Grun. ; 2V. modesta, 

 Grun. ; N. decurrens, var. Eh. var. subsolaris, Grun. ; 

 N. haueri, Grun. ; N. radiosa, var. dubraviccnsis, 

 Grun. ; N. gastrum, var. styriaea, Grun. ; A r . 

 dementis, Grun. j IV. tuscula (Eh.), var. ornata, 

 Grun. ; IV. elliptica, var. grandis, Grun. ; JV. 

 vcntricosa, var. truncatula ; N. informe ; JV. cruci- 

 cula, var. protracta ; Peronia antiqua, Grun. 



Staurosira Harrisonii, W. S. var. atnphitetras, 

 Grun. Frustule linear, valve quadrangular ; sides 

 concave ; apices produced, rounded ; striae cost ate ; 

 length of sides '0015, fig. 2. 



This charming little form is rare in the deposit. 

 The type form is, however, common. 



Fig. 42. — Surirella dementis, sss-. 



may be detected, and also a spinous median line. 

 This species is not uncommon in the deposit. 

 Synedra ulna (Ehr.) ; S. ddicatissima, W.S. ; 6". 

 familiaris, Kg., var. neogena, Grun. 



Nearly all the Synedras are more or less distorted, 

 apparently caused by pressure, and not by any terato- 

 genic influence exerted during the development of 

 the frustules. 



Nortvich, July, 18S4. 



A FREEZING MICROTOME. 



IN reply to E. Lamplough, I have' tried many forms 

 of freezing microtomes while working in the Strass- 

 burg laboratories, and got by far the finest sections of 

 soft tissue by using the one described below, which 

 was made from descriptions of one which I am told 

 is in use in Dr. Klein's laboratory. The freezing 

 vessel consists of a small wash-tub, twelve inches dia- 

 meter, by three and a half inches deep. Get a cover made 

 of wood on which is cemented a plate-glass top with 

 a hole cut in the centre, one and three-quarter inches 

 in diameter ; out of this hole projects slightly a brass 

 or iron grated top. (on which the tissue is frozen), this 

 top rests on a hollow pillar screwed on to the bottom 

 of the tub, and this pillar is honey-combed with holes, 

 to give free access to the freezing mixture with which 

 the tub is filled, viz., ice and salt. The microtome is 

 made on the principle of a joiner's hand plane, and 

 consists of a metal frame (brass is best) to hold three 

 large and fine threaded screws, A, B & C, which are 



