K()N(il. SV. VET. AKADEMIENS HANDUNGAR. RAND 34. v<> 8. <il 



The hypostoma has ;i large central ovate gibbosity with the maculae near its basis, 

 snrrounded by the winglike expanded limbus. 



Mogal. attenuata Wahlenberq. 



Pl. V figB. 1—6. 



The long .-nid oarrow maculse are crescent-shaped and projeel beyond the hypo- 

 stoma supported on the superior surface of ;i sharp extenuated edge where they resl as <>n 

 a shelf. They consist, as scen in vertieal sections, figs. 5, ii, oi' alternating rows of lighl 

 and black streaks, and in a horizontal section the spongious network appears, as it is 

 found in Asaphus and others and thns indicating the tendency of this organ t" assume 

 a prismatic strueture though undeveloped. 



The cephalic eyes in M. attenuata form the most regular hexaedral prisms lig. 1 a, 

 short and covered by m thin cornea. The horder zone of the eyes has a strueture <'\;iet]y 

 like that of the maculse, the same as in the spongious zone of Asaphus. 



Megal. limbata Boeck. 



Pl. V fig. 7. 



We give ;i new figure of Brögger's original specimens, as his figure 23, Tab. II 

 is incomplete and incorrect. The maculse are situated a little higher up on the sides of 

 the central gibbosity. 



- 



Megal. planiiinibata Ang. 



Pl. V tig. 8. 



The maculae are crescent-shaped and not so prominent as in Meg. attenuata and 

 the visual spöt in the same position as there. 



To observe is that the general strueture of the hvpostomic shell in this and many 

 other species is prismatic. 



Nileus Dalm 



an. 



Hypostoma with macuke figured in N. armadillo by Angelin pl. XVI tig. ."> c, and 

 Br. II pl. 3 fig. 40. 



The hypostoma in this genus is transversal with large lateral expansions, the central 

 convexity only faintly elevated and almost coherent with the posterior part. The maculae 

 lie exactly on the horizontal median line of the hypostoma. The anterior wings are 

 well developed like slightly bent acuminated horns and the posterior wings are conieal 

 points. The terrace lines are transverse and a little wavy. 



K. Sv. Vet. Akad. TIandl. Band 34. N:o 8. 8 



