BY G. I. PLAYFAIR. 189 



This is not a variety of St. dllatatum, for in that species, if the 

 underside of the semicell be focussed, 13 vertical rows of granules 

 can always be counted; the form above has only nine. Nor can 

 it be a form of St. fricorne^ which has four granules close together 

 in a square at the extreme end of the lateral angle and which 

 appear plainly as minute teeth in front and end views. Including 

 the apical four, that also has 13 vertical series. In the mature 

 form of any species the little details of ornamentation (such as 

 number and arrangement of granules, verrucae, etc.) are remark- 

 ably constant and afford the best clue to identification in some 

 eases. See note to St. campanulatum,, below. 



St. campanulatum, n sp. (T.v. f.8). > 



St. minutum, tarn longum quara latum, medio sinu minimo 

 constrictum. Semicellulae campanulatae, supra basin levissime 

 inflatae; lateribus pauUo sinuatis; dorso piano; angulis superi- 

 oribus in processus singulos horizon taliter productis, processibus 

 brevibus apicibus rotundatis interdum denticulis binis minutis 

 praeilitis. A vertice visae triangulares lateribus concavis, angulis 

 subacutis, apicibus rotundatis, granulis minimis in seriebus trans- 

 versalibus 6 ornatis. 



Long. = la t. 27-32/x. 



Rose's Lagoon, Collector. 



This form is to be classed with St. striolatum Nag., Einz. Alg. 

 T.8, f.A3; and St. dilatattim Ehr. var. i7isigne Kac, Desm. Ciast. 

 T.2, f. 13, both of which are also known here. 



St. patens Turn., Alg. E. Ind. p.l08, T 14, f.21, forma australica, 

 n.f. (T.v. f.9). 



Forma minor, a fronte visa ut a Turner I.e. delineate, aculeis 

 autem plerumque ternis. A vertice visa triangularis, lateribus 

 levissime concavis fere rectis, angulo quoque repente constricto et 

 in tubulum brevem, truncatum triaculeatum producto; area 

 central! granulis geminatis in seriebus 3 concentrice ordinatis et 

 angulos versus granulis binis ornata. Semicellulae interdum 

 alternantes. 



