136 hTOII\I lX, 017 ~Lk.kJ~~>lll‘t’~~. quality of definition over the dou1)le sgstern of reflecting prisms that lias becn proposed ; the gveutest thicliness of glass that the rays have to pass through beiug only *096or less than one tenth of an inch. The drawback to the adoption of the prism I have descrihed is the great difficulty attendant iipon its constrnction. The binocular iiiicroscope, in its principle to the present time, homwer carefully constructed, gives but little reason for expecting any particular discovery to result from its aid, as it fails in giving a distinct clefinition of test objects ~mder the highest powers, and must cwr fail in this particular, while only one half t’le ob,ject-glass is used in producing each image. With low powers, howcver, on objects having an apprcciable thickness, its perfornlaiice is sufficiently satisfac- tory. In the instriuniciit I now exhibit, all the adjustments beingfixed, it is not liable to get out of order, and mill bexr as much rough usage as any microscope. The double body can be fitted to any of the ordinary forms of niicroscope- stand, List of DIATOX~CE.Eoccurring in the nciyiiboiirliood of ~ITLL. By GEORGENORMAN, Esy., Hull. (Continued from page 71.) PIANULARIA,Ehrenberg. P. nobilis, Ehr.-In fresh-water ditches not common. Ditch Cottingliam. Road. Peat Deposit, Hornsea. P. nmjor, Sm.-Frequent in fresh-water ditches. Harrogate. Hornsea Peat Deposit. Market Weighton Canal. Spriiig Ditch. P. tii~idis,Sm.-Very frequent in fresh watcr. Spring Ditch. Cottingham. Saltersgate. Nettleton. Sliirlaugli. Drif- field. Iteservoir IVatcrworlis. Haltenyrice. IIoriiaea Deposit. Beverley. P. oblonga, Sin.-Frequent in fresh water. Cottiiigham. Spring Ditch. Sliirlangh. Hornsea Deposit. Pure in Springs near Cotting1ia:n. P. carrlimlis, E1ir.-Not unfrequent in the Hornsea Peat Deposit. P. distuns, Sni.--Very frequent in Ascidians. Sands at Hornsea. Dredgings off Flsrubro’ Head. XORMAK,on Diatoxncece. 157 p.percgrina, Ehr.-Very frequent in brackish water. Stone- ferry. Tetney. Humber Banks, very frequent. Copious and nearly pure in a ditch near River Hull, above Stone- ferry. P. acuta, Sm.-Very frequent in fresh water. Cottingham. Pond at Skirlaugh. Risby Pond. Driffield. Wawne. Market Weighton Canal. Spring Ditch. Beverley. P. directa, Sm.-Local. Frequent in a salt-water gathering, Grimsby . P. radiosa, Sm.-Very frequent in fresh and brackish water. River Hull, pure. Cottingham. Pure at Harrogate. Haltenprice. Pure in a Spring, Cottingham. Hornsea Peat Deposit. Reservoir Waterworks. P. gracilis, Ehr.-Very frequent in brackish and fresh water. Marfleet. Humber Banks. Pure in a ditch near River Hull. Tetney. Saltersgate. Spring Ditch. P. airidula, Sm.-Very abundmt in fresh water. Wawne. Killinghall. Abundant near Cottingham. Near Stone- ferry, Very pure near “ Ncm Village ” Cottingham. P. Cyprinus, Ehr.-Very abundant in salt and brackish water. Dairycoats, under Railway arch. Humber Banks, fre- quent. Marsh Chapel. Tetney. Grimsby. Very good in a ditch near the River Hull. P. divergem, Sm.- Rare. Cottingham, near Mr. Harrison’s Grounds. Ditch near Springs, Cottingham. P. stauroneifornzis, Sm.-Not unfiequent in fresh water. CO- pious in a gathering, sirlaugh. Nettleton. Reservoir Waterworks. Harrogate. Cottingham. Spring Ditch. P. Johnsonii, Var. p Sm.-Copious in a gathering from the Piers of the Victoria Dock. P. gibbu, Ehr.-Rare in fresh water. Saltersgate. Risby Pond. Cottingham. Haltenprice. P. Tabellaria, Sm.- Rme. Rocky stream, Saltersgate. P. mesolepta, Ehr.-Not unfrequent in fresh water. Boggy ditch, Saltersgate. Haltenprice. Hornsea Deposit. Be- verley Parks. p. nmolepta Var. with stauros.-Fresh water. Risby Pond. Harrogate. P. interrupta, Sm. - Not common. Nettleton. Wawne. Harrogate. P. interrupta, Sm. Var. P.-Rare. Clay Pits, Nettleton. P. borealis, Ehr.-Rare. Soil from nningholme Cam. Market Weighton Canal. Be, P. hemiptera, Sm.-Rocky stream, Saltersgate. P. gracillima, Greg.-Rare. In rocky stream, Saltemgate. P. Polyonca, I3rBb.-Very rare. In a pond in the wood at Nettleton. 158 L-ORMAX,012 Diatoiitrrcece. P. pypzcea, Ehr.-Not unfrequent. Banks of River Hull. Ditch at Cottingham. In a water tub for poultry. Sinall ditch near River Hull, above Stoneferry. Near the Glass Houses, Dr. Munroe. P. biceps, Greg.-Rare. Market TTieighton Canal. P. garganica, Rabenh.-Frequent in fresh and brackish water. Ditch leading from Anlaby to Hessle Road. Humber Banks. Ditch at Cottingham. Harrogate. Ditch near River Hull. STBURONEIS,Ehrenberg. X. Phoxicenteron, Ehr.-Common in fresh water. Nettleton. Cottingham. Saltersgate. Nearly pure in a boggy place, Sliirlaugh. Rishy Pond. Harrogate. Hornsea Deposit. Market Weighton Canal. S. gracilis, Ehr.-Not uncommon. Xear River Hull. Net- tleton. Haltenprice. Humber Banks. Spring Ditch. Hornsea Deposit. X. acuta, Sm.-Rare. Not unfrequent in Rishy Pond. Hornsea Peat Deposit. S. salina, Sm.-Frequent in brackish water. Pure near Stoneferry. Stallingbro’. Marsh Chapel. T’etney. Ditch near River Hull. Outlet Hornsey Mew. X. dilatata, Sm.-Rare in brackish water. Ditch near River Hull, beyond Stoneferry. Tetney. S. crucicula. Sm.-Rare in bracliish water. River Hull. X. anceps, E1ir.-Frequent in fresh water, though never abun- dant. Spring Ditch. Frequent near Cottingham. Be- verley. Nettleton, in Clay Pit. Wayne. Harrogate. Haltenprice. Hornsea Deposit. S. linearis, Ehr.-Frequent in fresh rater, though always much mixed. Iiillinghall. Bwerley. Very frequent near Cottingham. Market Weighton Canal. S. pulchella, Sm.-Very frequent in Ascidians. Hornsea Sands. Dredgings off Flambro’ Head. PLET‘ROSIGJIA,Smith. P. decorum, Sm.-Rare. Not unfrequent in a Dredging oil Flambro’ Head. P. rigidurn, Sm.-Rare in a Dredging taken off Flambro’ Head. North Humbcr Rank, Dr. Munroe. P. elongatum, Sm.-Abundant in salt n-ater. Ditch leading from Anlaby to Hessle Road. ?tladeet. Outlet Hornsea Meer. Ditch near River Hull. Tetney. P. intermediicm, Sm.-Not nnfrequent in salt water. Victoria Dock Timber Pond. Timber Pond, Grimsby. r\T~fi~~~~,on Dialomacece. 159 p. Nubecula, Sm.-Rare. Timber Pond, Grimsby. Timber Ponds, Victoria Dock. P. delicatulum, Sm.-Not unfrequent in salt and brackish water. Victoria Dock Timber Ponds. Ditch leading from Stoneferry to Sutton. p. striyosum, Sm.-Not unfrequent in salt water. Humber Banks, near Paull. Dredgings, Flambro’ Head. Grimsby. Humber Banks, Marfleet. p. quadratum, Sm.-A small variety in abundance under the Railway arch, Dairycoats. p. anyulatum, Sm.-Very frequent and abundant. Humber Banlrs. Garrison Moat. Dairycoats. Pure in many instances. Outlet Hornsea Neer. Stoneferry. Grimsby, very large. p. Bstuavii, Sm. ?-Plentiful in a gathering under the Rail- way arch, Dairycoates. North Humber Bank, Dr. Munroe. p. Normani, Ralfs =lanceolatum, Nor.-Abundant in Ascidian gatherings. P. lanceolahn, Donk.-Very rare. Sand at Hornsea. P. ucutum, Nor. M. S.-Frequent in Ascidian gather- ings. P. Balticum, Sm.-Very rare. Humber Banks in two in- stances, but only in odd frustules. P. sca@rum, Br6b. =Balticum, Vur. y Sm.-Frequent in salt and brackish water. Pure on a stone Jetty near Hessle. Grimsby. River Hull. Humber Banks. Garrison Moat. Ditch near River Hull, above Stoneferry. P. Xtriyilis, Sm.-Not unfrequent in salt and brackish water. Pure, Humber Bank, near Marfleet Clougli. Ditch near River Hull, beyond Stoneferry. Ditch running from Stoneferry to Sutton. P. acuminutum, Sm.-Not unfrequent in salt water. Near Grimsby. Stallingbro’. Never abundant. P. distortuna, Sm.-Not common. Salt or brackish x-ater, near Grimsby. P. Fasciola, Sm. -Very frequent in brackish water. Humber Banks, very frequent and sometimes pure. Garrison Moat, pure. Grimshy, much larger than on the north side of the Humber. Ditch running from Stoneferry to Sutton, pure. p. macrum, Sm.-lTery local. Copious in a brackish ditch running from Stoneferry to SuttQn. p.prolongatum, Sm.-Pool at Grimshy, rare. Not unfrequent in Ascidian gathcrings. Victoria Dock Timber Pond, Mr. Robt. Harrison. p. transversale, Sm.-Rare. In Ascidians. 1GO NORMIY, OIL Diuioniacecr. P. tenuissimum, Sm.-Rare. Not uiifrequeiit in a large POL of salt water near the Dock, Grimsby. P. littorale, Sm.-Rare.-Mised with P. angulatum. Shores of the Humber, between Grimsby and Stallingbro’. P. Hippocampus, Sm.-Very frequent in salt and brackish water. Pure on Humbcr Banks. Garrison Moat. River Hull. Tetney. Ditch near River Hull, above Stoneferry. P. attenuatunz, Sm.-Very abundant in fresh water. Spring Ditch. Pure at Haltenprice. Cottingham. Nettleton. Risby Pond. Newbald. Frequent in Hornsea Peat. Market Weighton Canal. \Tame. P. attenuatum, Sm. Var P.-Frequent in fresh water. Reser- voir Waterworks. Wawne, &c. P. lacustre, Sm.-Abundant in fresh v-ater. River Hull. Cottingham. Risby Pond. Ripley. Harrovgate. Haltenprice. Hornsea Peat. Beverley. Market Weighton Canal. P. Spewerii, Sm.-Frequent in fresh water. Spring Ditch. Hornsea Meer. Wawne. Risby Pond. Clay Pit, Nettleton, very good. Haltenprice. Hornsea Peat Deposit. P. Parkerii, Ham.-Copious in a fresh-water gathering from Thornton-le-Moor. TOXONIDEA,Donkin. T. insignis, Donk.-Rare in Ascidian gatherings. T. undulata, Nor. $1. S.-Very rare in an Ascidian gathering. SYNEDRA,Ehrenbergh S. pulchella, Kiitz.-Not common. Salt and brackish water. Humber Banks. Reservoir Waterworks. S. gracilis, Kutz.-Nat unfrequent in brackish ditches. North Humber Bank. S. acicularis, Sm.-Frequent in salt and brackish water. Humber Banks. Tetney, in large pool of water near the Lock.