LAGANUM BONANI. 517 



Laganum Bonani 



! Laganum Bonani Kl., 1734, Nat. Disp. Ech. 



PL XIII'. f. 6-7. 



The outline of this species is pentagonal, the longitudinal diameter 

 slightly greater than the transverse ; the posterior edge of the test is trun- 

 cated, slightly re-entering. The greatest transverse diameter is slightly in 

 advance of the apex, in a line with the anterior extremity of the anterior 

 ambulacra. The test is thin, but the edge is greatly swollen, so that the 

 apex rises but slightly above the edge ; there is frequently a marked depres- 

 sion of the test between the summit and the edge. The apical system is 

 small. The petals are large, extending to a short distance from the edge ; 

 they are lanceolate, nearly closed at the extremity ; the five genital pores 

 are in close proximity. The poriferous zones are narrow ; the pores closely 

 packed together, and connected by distinct grooves, the outer pores far the 

 largest. 



The posterior pair of petals are somewhat longer than the anterior pair ; 

 these in turn are slightly shorter than the odd petal, which has a narrower 

 interporiferous space than the other ambulacral petals. 



The tuberculation is remarkably uniform, the tubercles of the lower sur- 

 face somewhat larger and more separated than those of the abactinal side ; 

 miliaries small and indistinct ; the ambulacral furrows broad, marked, ex- 

 tending more than half-way between the actinostome and the edges of the 

 test ; the ambulacral pores are especially numerous near the actinostome. 

 The anus is large, longitudinally elliptical, placed about half-way between the 

 actinostome and the edge of the test ; the anterior edge depressed. The 

 mouth is large, pentagonal. The spines are uniform, those of the upper part 

 of the test short, slightly club-shaped, while those of the actinal side are more 

 slender and fluted. The few spines immediately around the actinostome are 

 particularly long and slender. In a series of alcoholic specimens preserved 

 in the Jardin des Plantes the color is brownish-yellow, witli small round 

 patches of black irregularly scattered on the interambulacra of the upper 

 side of the test. The partitions of the interior are limited to a couple of 

 thick concentric walls, diverging from the median interambulacral pillars, 

 which radiate from the edge. 



Tasmania ; East India Islands ; Philippine Islands. 



