206 Dr. T. Wright on the Cassidiilidfe of the Oolites. 



Extremely variable in size and in the colour of the elytra; spe- 

 cimens ocpur of various shades from rufous to black. 



The two foreign insects in the cabinet of Mr. Kirby sent by 

 Gyllenhal, with the name '^ Carpini/' agree with British speci- 

 mens. I possess a foreign insect from Dr. Germar named Aca- 

 lyptus rufipennisj which I have no doubt is a variety of this, 

 having pale elytra. 



First discovered as a British insect by Mr. S. Stevens, who 

 found it whilst beating the sallow blossoms, on the 28th of April, 

 in a small wood near Fenny Stratford ; to whose liberality I am 

 indebted for specimens. 



XVIII. — On the Cassidulidse of the Oolites, with descriptions of 

 some new Species of that family . By Thomas Wright, M.D. 

 &c.* 



[Continued from page 103.] 



Genus Dysaster, Agassiz. 



Test ovate or subdiscoidal ; ambulacra simple, continuous and 

 radiant ; the posterior pair separated from the others, and con- 

 verging to form a summit at some distance behind that formed 

 at the apical disc by the antero- lateral pair and anterior single 

 ambulacrum which gives value to the name Dysaster. Upper 

 surface of the test smooth and convex, under surface much undu- 

 lated from the convexity of the interambulacra and the straight- 

 ness of the ambulacra. Tubercles small, mammillated and per- 

 forate, and surrounded by a circular depression ; apical disc situ- 

 ated at the junction of the three anterior ambulacra, and formed 

 of four perforated ovarial plates which are intimately soldered 



* I have dedicated Pygaster Morrisii to my friend John Morris, Esq., 

 one of the learned authors of a Monograph of the MoUusca of the Great 

 Oohte. 



After the first part of this papeT was printed, I met with a specimen of 

 Hyhoclypus caudatus with the apical disc preserved in situ, which I regret 

 was not found before the plate containing the details of the anatomy of 

 that species was completed. The disc is formed of two small anterior ovarial 

 plates, the right plate supporting the madreporiform body, and two larger 

 posterior ovarial plates ; between them and occupying the centre of the 

 disc are four small rhomboidal plates, which probably represent the single 

 ovarial plate composed of two valves, and the two posterior ocular plates 

 displaced from their normal position in consequence of the posterior pair 

 of ambulacra terminating in this genus at a short distance behind the apical 

 disc ; at the summits of the single and anterior pair of ambulacra are three 

 small ocular plates with distinct eye-holes ; the posterior ambulacra have no 

 ocular plates at their summits ; these elements according to my view are 

 transposed to the centre of the disc to give greater expansion to the struc- 

 ture in this region. 



