242 MESSKS. W. AVEST A^D G. S. WEST O^ 



of the sinus, the apical incision, the basal protuberances, and the thickened angles it 



must of necessity be placed under the genus Euastnim. As it has only been imperfectly 



described, we append the following amended description : — 



U. permagnum, circiter 3-|-plo longius quam latins, modice constrictum, sinu lineari ; 

 semicellula? longitudinaliter oblongse ; angulis inferioribus rectangularibus et 

 levissime rotundatis, lateribus leviter convexis, vel convexis in parte inferiore et 

 concavis in parte superiore, vel concans in parte inferiore et convexis in parte 

 superiore, apicibus snbrotundatis vel trnncatis cum angulis rotundatis, interdum 

 apices versus subito attenuatis, incisura mediana profunda et angustissima, intra 

 angulos inferiores tumore, supra isthmum tumore instructa ; a latere visae lingui- 

 formse, angulis basalibus rectangularibus et levissime rotundatis, aj)icibus rotundatis ; 

 membrana scrobiculata ; angulis inferioribus et incisuris apicalibus valde incrassatis. 

 Long. 248-251^; lat. 73-77 a*; lat. isthra. 32-34-5 /*; crass. 73^1. 



49. EuASTRUM CEASSUM, Kuetz. ; Ralfs, Brit. Desm. p. 81, t. 11. fig, 3. 

 Var. scROBicuLATTJM, Lund. Desm. Suec. p. 18, t. 2. fig. 1. 



o o o o 



^O o o ^ o o oo 



Fig. 1. — Euastrum crasmm var. scrohiculatum, Lund. — Central scrobiculations. 520/1. 



Lundell describes the scrobiculations as one or two; they vary in the American 

 examples we have seen from one to six. (Fig. xyloo-r. 1.) 



50. E. OBLo^GrM, Ealfs, Brit. Desm. p. 80, t. 12. 



Eorma scrobiculata, l^ordst. Sydlig. Norges Desm. p. 7. 



Tbe scrobiculations of this form are much smaller than those in the var. of K crassim; 

 the number in tbe centre of each semicell is one or two in tbe American specimens 

 examined. 



51. E. INSIGNE, Hass. Brit. Ereshw. Alg. p. 21, t 41. fig. 2 ; llalfs, Brit. Desm. p. 83, 



t. 13. tig. 6. (PI. XIV. fig. 17.) 



Long. 133^; lat. 69-75 Ai; lat. isthm. 17 ^t; crass. 36 /x. 



Typical examples of this were frequently observed; we note this because the figures 

 given by Wolle (Desm. U.S. pi. 27. figs. 39-43) do not represent the species, but are 

 probably A. orientale, W. B. Turn. Before we had seen the remarks under the last-named 

 species by Turner (Ereshw. Alg. of E. India, p. 79) we had written a long note practically 

 embodymg the same conclusions concerning E. mamillosum, Wolle, Desm. U.S. p. 102, 

 pi. xxvi. figs. 14, 15. 



52. E. INTERMEDIUM, Cleve, in Ofvers. Sv. Vet.-Akad. Eorh. 1863 (1864), n. 10, p. 484, 

 t. 4. fig. 1 ; Lund. Desm. Suec. p. 21, t. 2. fig. 4. (PI. XIV fio>s 18 19 ) 



Long. 60-66^; lat. 38-5-42 ^; lat. isthm. 7-5-8 ,,; crass. 16-5-18% ^ ' 



