244 



ciful and elegant markings, Plate XIII. Fig. 60. Rosinus describes 

 several varieties of this species of asteriae, Tab. IV. et V. usque ad 

 class um, M. In some of these species, the petal-like rays obtain 

 somewhat of a curved form ; and in others, a flowret is disposed on 

 the centre of the star already mentioned. With respect to their sides, 

 they may be seen to tend in every degree to a pentagonal form. In 

 some the circumference is formed by five slightly curved lines, united 

 at angles hardly perceptible, Fig. 61; whilst in others the curvatures 

 become much greater, Fig. 62 ; and in some a considerable indenta- 

 tion is formed on each of the five sides ; giving to the body an ap- 

 proach to the stellated form, as in Fig. 63 and 65, and increases in 

 different specimens, as in Fig. 64 and 67 until it is found to form the 

 complete five-rayed star, Fig. 66. 



All these, as may be seen in the respective figures, differ again 

 considerably, in the form of their rays, and the disposal of their 

 markings. In one species, Fig. 68, these indentations, on a margin 

 approaching to the circular, are so sudden, and comparatively so deep, 

 as to give a truncated appearance to the ends of the rays. The mar- 

 gin of this asteria is finely crenated, and being a little raised, the 

 star is imbedded in a small concave depression. 



Bourguet describes a species, which instead of being marked with 

 five petals, has five circular holes or cavities, at equal distances round 

 the central foramen *. 



Rosinus, Hofer, Wolfart, and others, have spoken of asteriae with 

 four sides and four rays. The only one of this kind which I have 

 ever seen is depicted Fig. 59. Too little, however, is known respect- 

 ing asterire of this form, to enable us to determine whether this should 

 be considered as marking a difference of species, or that of a variety 

 only. The former supposition, however, appears to be the most pro- 

 bable. 



. 



* Traite des Petrifactions, Tab. LVIII. No 425. 



