SOME ^^ORTH AMERICAN DESMIDIE.E. 241) 



convex towards each other, but slightly concave. The central tumor is not so elevated, 

 and is not granulate but scrobiculate. 



Var. DEPEESSTJM, nov. var. (PL XV. fig. 23.) Var. semiccllulis depressis, sinu minus 

 aperto extremo valde ampliato, apicil)us subtruncatis, dcntibus ad apicom paulo 

 infra marginem posit is, angulis inferioribus dentibus 0-6 intra marf^inem irre- 

 gulariter dispositis. 



Long, sine dent. 77-86 ^i; lat. sine dent. 5 i-05 /t; cum dent. 63-73 n ; lat. isthm. 17-25 /t. 



We have met with this variety much more often than with the type. 



78. CosMARiTJM DENTATUM, WoUe, Dcsm. U.S. p. 70, pi. 13. fig. 15. (PI. \\. 

 figs. 10, 11.) 



We presume that Wolle has observed the same plant that we have seen ; yet, as neither 

 his description nor his figure represents the species correctly, we give both. 

 C. magnum, 1^-plo — subduplo longius quam latins, profunde constrictum, sinu aperto 

 apice acuto ; semicellulse late ellipticjc vel subrotundfc, apicibus leviter subtruncatis 

 [vel late rotundatis (Wolle)], lateribus dentibus subobtusis 10-12, aliis paucis intra 

 marginem, in centro incrassattie ; a vertice visa? ellipticae, ad medium utrobique 

 valde incrassatsB, ad polos dentibus 3-4 et dentibus irregulariter ordinatis in zonA, de 

 polo ad polum, in centro defectis; a latere visas circulares vel late ellipticas; 

 membrana crassa luteola, minute scrobiculata, scroliiculis majorilnis in parte ccntrali 

 incrassata, inter scrobiculos minutissime et dense punctulata. 

 Long. 135-169 ^i ; lat. sine dent. 88-96 ^ ; lat. isthm. 31-33 a* ; crass. 66-69 ^. 

 The membrane is finely scrobiculate and not " closely set with small pearly granules." 

 Wolle states in his description that there are from 10 to 12 teeth on each lateral margin 

 of the semicells ; his figure shows 17 to 18, and these are figured proportionally too small. 



79. C OVALE, Ealfs, Brit. Besm. p. 98, t. 15. fig. 9. 



Var. SUBGLABRUM, uov. var. (PL XV. fig 3.) Var. granulis perpaucis, duobus (fere) 

 ad angulum basalem unumquemque, 3-4 apices versus utrobique et 2-3 intra 

 marginem prope apicem, apicibus anguste truncatis ; membrana magis scrobiculata 

 ut in forma typica. 

 Long. 154 ju ; lat. 88 ^ ; lat. isthm. 30 /t. 



A common American form of this species has a slightly subtruucate and retuse apex, 

 with the retuse portion without granules ; in this respect it approaches var. excisum, 

 Racib. in Pamiet. Akad. Krak. xvii. (1890) p. 91, t. 6. fig. 2. 



80. C. BALTEUM, nov. sp. (PI. XV. fig. 1.) C. submagnum, lf,-plo longius quam 

 latins, profunde constrictum, sinu angusto-lineari extremo subampliato ; semicellulae 

 truncato-pyramidatiie, lateribus convexis, angulis inferioribus superioribusque rotun- 

 datis, apicibus levissime convexis, margine granulato-undulatae ad apicem granulis 

 reductis, granulis magnis in seriebus concentrice 3 intra marginem (seric interiore 

 majore), sinus versus granulis minorihus et subirregularibus ; ad medium supra 

 isthmum granulis parvis paucis in seriebus horizontalibus 4 dispositis ; a vertice 

 visae ellipticse, polis granulato-undnlatis, de polo ad polum cum zona lata granulorum 



