crick: on plesioteuthis prisca. 317 



regarded bj' Wagner as referable to the same species.^ The type came 

 from the l)eutingeu Quarry, near Mohnheim, 



The other species, Plesioteuthis acuta (3, p. 64, pi. rii, figs. 4, 5) 

 Avas originally described by Miinster as an Acanthotetithis. 



In the original description, in 1829, of the species P. prisca, Ruppell 

 (5, p. 9) referred to the presence on the dorsal side of a heart-shaped 

 swimming membrane, about one-fifth of the length of the whole 

 mantle, and, from his figure, it would seem that he was alluding to 

 the expansion at the posterior end of the body, surrounding the lance- 

 shaped posterior extremity of the gladius to which he also refers. _ It 

 would appear that this expansion of the gladius was fairly flexible, 

 because in several examples in the British Museum collection that 

 exhibit a lateral aspect of the animal the posterior part of the pen is 

 evidently folded upon itself along the median line. 



The lance-shaped extremity of the gladius was figured by Miinster 

 (3) in several Teuthids from the Lithographic Stone of Bavaria 

 (pi. iv, figs. 6, 7 ; pi. V, figs. 1-5 ; and pi. vi, fig. 3) ; but none of 

 these were named. Of these the one most nearly resembling the 

 present specimen is the original of pi. v, fig. 3. So far^ as the 

 present writer is aware, the presence in this genus of terminal fins 

 has not yet been recorded. 



The genus Acanthoteuthis was instituted by R. Wagner (in Miinster, 

 1, pp. 92-4) in 1839, and subsequently Miinster (3, pp. 56-9) 

 recognized three subdivisions of the genus, viz. (1) Acanthoteuthis, 

 sens, str., (2) Doryanthes, and (3) Acantho2nis. The figures above 

 mentioned would all belong to his section Boryanthes (p. 58), but 

 there seems to be no allusion to them in the text, and they are not 

 named in the explanation of the plates. This is to be regretted, 

 since one example (pi. v, fig. 3) exhibits, at the anterior end, 

 structures to which one would like to have seen some reference. One 

 of these — the posterior — is very similar to the structure of the anterior 

 end of the median portion of the gladius in the present specimen. It 

 is, however, to be noted that Miinster's figure, judging from the 

 presence of the ink-bag, represents the ventral surface of the gladius, 

 from which structure it is quite distinct, although the anterior 

 boundary of the gladius is not very clearly shown. 



Although the present example exhibits features which have not 

 hitherto been observed in the genus Plesioteuthis, it is not proposed 

 to establish a new genus for it, nor even to regard it as a new species, 

 but to consider the specimen as an example of Plesioteuthis 2>risca in 

 a better state of preservation than any specimen previously described. 



^ The synonyms mentioned by Wagner (6, p. 816) were as follows : — 



" Acanthoteuthis angusta, brevis, intermedia, lata (partim), rhomboidalis, 

 sagittata, semistriata, stibconica, subovata, and tricarmata, Miinst. 

 Lo%o jjmca,Kupp. ; L. subsagittata, Miinst. ; Enoploteuthis subhastata, 



d'Orb. 

 Ommastrephes angustus, sagittatus, intermedins, and cochlearis, d'Orb." 

 To these may be added the LeptoteutJiis gracilis of Owen (4, p. 3), from the 

 Lithographic Stone of Solenhofen, near Pappenheim, Germany, which the 

 present writer had an opportunity of examining in 1887. 



