508 PROFESSOR GREGORY ON 



these plates in four species, all of which have the general aspect of Amphiprorce, 

 naturally leads to the inquiry, whether this remarkable structure may not be 

 found in all the species of the genus, or whether the forms in which it occurs 

 ought not to form a new genus. I understand from Mr Roper, that he has found 

 this species in a marine gathering from the coast of Wales, or of the south of 

 England. 



62. Amphiprora (?) complexa, n. sp. PL XII. , figs. 62 ; 62, b ; 62, c ; 62, d\ and 

 62, e. Form elliptical, broad, with a constriction in the middle, and broadly rounded 

 ends. The frustule is composed of two arcuate and constricted segments, which 

 are broad, thick at the outer margin, thin at the inner margin, and placed oppo- 

 site each other, with a narrow interval between them. Over the middle of these 

 two lateral segments is placed a complex mass, formed of five or six segments, 

 converging inwards and on the ends, like the segments of an orange or melon. 

 The thick backs of these central segments, marked with transverse stria?, are 

 alone seen in the entire frustule, and those of the outer segments approach near 

 to the outer margins of the lateral or flat lying segments, leaving only part of 

 the surface of the latter exposed. A convex line joins the convergent ends of the 

 central segments 



When the frustule, as often happens, falls asunder, a number of segments are 

 found lying near each other. Some of these have no constriction, and no nodule ; 

 these I take to be the segments of the central mass. Those with nodules at the 

 middle of their outer margin, at the constriction, seem to be the lateral seg- 

 ments. 



Length of frustule 0-0035" to 0-004" ; breadth 0-0028". Segments arcuate, broad ; 

 some with a nodule and constriction on the thick convex or outer margin, others 

 without. Surface of segments finely striated; striae about 45 in 0-01, delicate, 

 radiating from the thin or inner margin, and curved near the ends of the segment. 

 At the margin, there is a row of conspicuous puncta, about 1 for every 2 striae. 

 The backs of the central segments, when in situ, are striated, but exhibit neither 

 nodule nor puncta. 



It is with much doubt that I refer this very curious form to Amphiprora; 

 which I should not do, were it not that the lateral plates in four species already 

 described may be regarded as the rudiments of the complex central mass in 

 this species. One of the three alluded to, Ap. plicata, has even longitudinal folds 

 in the middle part. 



It is, however probable, that the remarkable structure of this species may 

 render necessary the establishment of a new genus, a step which I do not venture 

 to take without farther inquiry. 



This form, like the preceding one, first caught my eye in the Glenshira Sand, 

 where I could find, however, only detached segments, and one half frustule. Not 

 being able, from these, to understand the structure, and not, indeed, perceiving the 



