'37 



Crisina D*Orbigny. 



Crisina D'Orbigny, 1850, "Prodr. Pal. Stratigr.", II, p. 265 (nomen nu duin). 



Crisina D'Orbigny, 1853, "Pal. Frang. Terr. Crét.", V, pp. 912, 728. 



Crisina Neviani, 1900, "Monogr. Gen. Idmonea", Parte II, Cap. 1, p. 65. 



(nee Crisina Gregory, 1899, "Cat. Foss. Bry. Brit. Mus.", "Cret. Bry.", I, p. 159.) 



Crisina, as I use it in this Report, differs from the erect species of Tubu/ipora {Idmonea 

 auctt.) in the development of cancelli, specially in longitudinal lines along the basal surfaces of 

 the branches. These cancelli are developed in the earliest stages of the growth of the branch in 

 the recent C. radiaus, the ovicells of which differ from those of typical "Idmonea" in possessing 

 curious lateral porous windows. 



The history of the generic names Crisina and Crisisina has been given by Gregory 

 (t. cit., p. 159, note) ; but I do not find myself able to agree with him in his conclusions. 

 Gregory considers that D'Orbigny used Crisina and Crisisina indiscriminately, and that the 

 employment of the latter term was probably due to a misprint. I think, on the contrary, that 

 there is clear evidence that D'Orbigny meant to distinguish the two genera, and that there is 

 reason for accepting Crisina as he defined it. 



In the "Prodrome", Vol. II, p. 175, D'Orbigny defines Crisisina as follows : — "C'est 

 une Idmonea, dont les branches sont libres au lieu d'ètre fixes ". Crisina occurs on p. 265 of 

 the same volume, five species being mentioned. Xo diagnosis is given; and Crisina thus appears 

 to be a nomen nudum, so far as this publication is concerned. Gregory is perfectly 

 correct in stating that the species of both genera occur under Crisisina in the Index of the work 

 (Vol. III, 1852, p. 51); but a careful examination of this index shows that there are several 

 other mistakes in it, so that too much stress need not be laid on the omission of Crisina. That 

 D'Orbigny intended, even in this work, to keep the two genera distinct is indicated by the fact 

 that Crisisina and Crisina appear with two separate generic headings on p. 265 of Vol. II. 



In his larger work ("Pal. Frang.", p. 728) D'Orbigny states that he had given the name 

 Crisina to the species with erect branches, when he would have been more accurate in stating 

 that Crisisina was the name referred to ; while on Plate 612 he uses Crisisina in one place 

 where the text shows that he meant Crisina. But his real meaning may be inferred by noticing 

 that in this work he entirely suppresses Crisisina, placing species referred to it in the smaller 

 work under Idmonea, and stating specifically (p. 728) that he now places species with free 

 branches and without inferior pores in Idmonea, and that he retains Crisina for species "dont 

 la face inférieure est criblée de pores spéciaux". 



A comparison of D'Orbigny's two works with regard to the treatment of the five species of 

 Crisina mentioned in the "Prodrome" confirms the above conclusions. The facts are as follows : — 



"Prodrome", Vol. II. "Pal. Frang. Terr. Crét.", Vol. V. 



Crisina unipora p. 265. Idmonea unifora p. 737, PI. 613, figs 1 — 10. 



Crisina rainosa p. 266. Idmonea ramosa p. J36, PI. 611, figs 11 — 15. 



Crisina Normaniana p. 265. Crisina Normaniana p. 914, PI. 612, figs. 1 — 5. 



Crisina sub gr adat a p. 266. Crisina subgradata p. 914, PI. 612, figs 6 — 10. 



Crisina triangularis p. 266. Crisina triangularis p. 915, PI. 612, figs ii — 15; PI. 614, figs 11 — 15; 



PI. 769, figs u — 14. 



137 



SIBOGA-F.XrEDITIE XXVIII a. iS 



