chap, xvii.] VARIATIONS IN CMNOIDS. 437 



58. Actinometra paucicirra : 4-rayed specimen, ibid. " In. all 

 these [Nos. 657 and 658] the anterior ray (A) is missing, so that the 

 mouth, instead of being radial in position is placed interradially between 

 the rays E and B." Carpenter, I. c. 



Compare the following case of imperfect change towards the 4-rayed 

 state : 



59. Cupressocrinus crassus : abnormal calyx (now referred to this 

 species, see Bather, I. c, p. 169) has one segment of the calyx reduced 

 in size and bearing no radial plate or arm. This reduced segment is 

 covered in by the adjacent segments so that the calyx as a whole is 

 regularly 4-sided. Goldfuss, Nova Acta Ac. C. L. C, 1839, xix. p. 

 332, PL xxx., figs. 3 a and b [cp. No. 665]. 



Six-rayed varieties of five-rayed forms. 



Actinometra pulchella : doubtful case of six rays, Carpenter, 

 I.e. 



Antedon sp. Six-rayed specimen. " The additional ray is in- 

 serted between the two of the right side (D and E)." Carpenter, I. c. 



Rhizocrinus lofotensis : 6-rayed specimen. Four and six rays 

 stated to be more common in Rhizocrinus than in other recent Crinoids ; 

 seven rays are also found, but very rarely. In Pentacrinus no 6-rayed 

 specimen seen. Carpenter, P. H., Chall. Hep., xi. Pt. xxxn. p. 38, 

 PL viii. a, figs. 6 and 7. 



Pentacrinus jurensis (probably) : stalk with 6 sides. [Fig. 

 represents two adjacent lobes of the stalk as smaller and closer 

 together than the rest, suggesting that perhaps these two may cor- 

 respond with one lobe of the normal.] de Loriol, I.e., PL cxliv. fig. 7. 



P. jurensis : 6-sided stalk having two adjacent lobes larger than 

 the others, ibid., fig. 10. 



The following is a case of imperfect change towards the six-rayed 

 state : 



Sphaerocrinus geometricus : abnormal specimen having the 

 basal plate irregularly six-sided by reason of the flattening of the 

 external angle of an infra-basal piece. Three of the sides are normal 

 and each of these bears a normal parabasal ; but of the other three 

 sides two are rather shorter than the normal sides and each of them 

 bears a somewhat smaller parabasal. Upon the sixth side between 

 these two, is a still smaller parabasal. The radials are five as usual, 

 but one of them articulates with the smallest parabasal and in con- 

 nexion with this its form is changed [for details see original figure]. 

 Sculpture, &c. normal. Eck, H., Verh. naturh. Ver. preuss. Rheinl., 

 1888, Ser. 5, v. p. 110, fig. 



Three-rayed and five-rayed varieties of a four-rayed form. 



*36. Tetracrinus moniliformis: normally 4-rayed (as shewn in 

 Fig. 131, I.). A 3-rayed basal from the same locality, Birmensdorf 

 (Fig. 131, II.). A 5-rayed basal from Oberbuchsitten (Fig. 131, 



