NOTES ON SOME ABNORMAL FORMS OF AULACODISCUS, • 101 



six rays had four of these normal ; of the two remaining, that on 

 the larger accessory inflation is distinct with the rows in contact, 

 that on the smaller hardly differentiated. A third valve, also with 

 six primary rays, had two of these normal, but the remaining in 

 two unsymmetrical pairs (PL 281, fig. 7) : a beautiful case of sym- 

 metrical arrangement was, however, observed on a fourth valve, 

 shown on fig. 8 of PL 281, where two of the six rays standing opposite 

 to each other are straight and end in contiguous rosettes, whilst the 

 two others passing to each rosette are similarly curved in opposite 

 directions, the crescents and inflations at the outer ends of all being 

 of similar size and form, and quite normal. 



A specimen with three primary rays (PL 281, fig. 4; showed two 

 of these straight at right angles, and ending in an inconspicuous 

 rosette; the third curved away from that adjacent to it, and ending 

 m a second similar rosette. Valves with two rays were observed : 

 the rays being straight and at right angles, but proceeding from an 

 excentric point (PL 281, fig. 3). Only one valve has been seen with 

 a single ray, which also started from an excentric point (PL 281, 

 fig. 2). Of the two valves seen with no rays, the one showed the 

 regularly quadrangular outer edge of the elevated central portion 

 indicating the position of the absent rays (PL 281, fig. 1) ; on the 

 border of the other was an elongated elevation with convex surface, 

 and irregularly bent linear markings. 



Among the specimens procured by Kitton from Monterey, the 

 gaps in this curious series from Vera Cruz are filled up. Thus one 

 valve with five primary rays had three on one half of the valve, 

 meeting at a central rosette ; two on the other half were un- 

 symmetrical, and met at an obtuse angle in a second excentric 

 rosette. Another valve with four rays confined to one of its halves 

 showed three meeting in a common rosette, and the central portion 

 of the fourth curving to an irregular excentric clear space ; and 

 finally, a valve with three rays confined to one half, but in other 

 respects normal. 



itaceus 



found. Thus a Pisagua valve with seven rays had four of these in 

 Pairs towards opposite sides of the valve, whilst a 'Gazelle' speci- 

 men showed two contiguous rays separated by but a single row of 

 markings. It has also been found that a Yokohama valve with 

 seven rays had two in one half of the valve contiguous, and formed 

 b y three almost parallel rows. 



formcmts from Iquique the prin 



than 



Peripheral ; and in a specimen from Palillos guano one of the 

 Primary rays, though connected with a process, is without a sub- 

 jacent inflation— one of the inflations adjacent being without its 

 j' a y and process. Finally, in a valve of A. Rittrayii from the 

 u amaru deposit with four primary rays, two are almost at right 

 Titu* a third is afc a greater, and the fourth at a less acute angle ; 

 * ntth Assure-like ray similar to the other four is present, but has 

 process or clear space at its outer end. 



«• Processes. — These are absent in A. ttpsdicdlutits, A. Mt tjwmfcM, 



