TESCH— PTEROPODA AND HETEROPODA 183 



Gegenbaur notes in his specimens ten to twelve gills ; I myself found no more than 

 eight. 



The rounded whitish spots with a filament in their centres, as they are generally 

 found in Pterotrachea, and also mentioned by Gegenbaur in this species, seemed to be 

 quite absent in my specimens, as I found no trace of them. 



Recently a new species, Firola gegenbauri, has been described by Vayssiere* which 

 in my opinion is identical with Gegenbaur's species ; indeed Vayssiere himself, though 

 denying the identity, alluded to the close resemblance of the two forms, on account of 

 the cutis on the anterior part forming at either side a large lobe, hanging down from the 

 body, without being connected to that of the opposite side ; moreover toothed crests in 

 the region of the visceral nucleus and denticles on the tail are particularly mentioned as 

 characteristic features. The same is shown in fig. 1. It is remarkable that Vayssiere 

 notes no less than twenty-two gills. 



To confirm my suggestion that Pt. scutata and Pt. gegenbauri are identical, I have 

 prepared the radula and sought after the palatinal teeth. As to the first, I counted 

 30 rows (25 according to Vayssiere), with the usual formula 2. 1. 1. 1. 2. All plates in 

 a transverse row quite agreed with those represented in Vayssiere's figure t- The breadth 

 of the central plate I found three times the length of the same ; the measurements of this 

 plate in the 5th row are f of the corresponding one in the 16th row ; on account of this 

 exact agreement with Vayssiere's statements, I have thought it superfluous to figure the 

 radula again. 



The peribuccal teeth (fig. 3) form a very remarkable character of this species ; they 

 also have been mentioned by the French author. On the large muscular fold at the roof 

 of the buccal cavity I noted six palatinal teeth, the proximal ones very inconspicuous 

 (Vayssiere found five such teeth at either side). The peribuccal teeth are very numerous, 

 situated at the lips, chiefly crowded together at the dorsal and ventral halves. A single 

 somewhat larger tooth is placed dorsally, just on the median line. On the dorsal side there 

 are three indistinct rows ; laterally the teeth are more scanty ; towards the ventral half 

 they even entirely disappear, but form on the ventral region an isolated small group. All 

 these teeth are slender and feebly curved. Here again I must mention a difference between 

 my observations and Vayssiere's description, according to which the peribuccal teeth are 

 most numei'ous dorsally and laterally. This curious armature of the buccal cavity has as 

 yet been found only in this species and in Pt. talismani Vayssiere. 



Subgenus Euri/ops Tesch. 



18. Pterotrachea (Euryops) mutabilis Tesch. (Plate 14, fig. 4.) 



Stat, kk (1), Desroches Atoll, Amirante Group. A single specimen ($) with a total 

 length of 40 mm. 



The excellent preservation induces me to give a figure, to complete my former descrip- 



* Mollusques Heteropodes de " l'Hirondelle" et de la " Princesse Alice," Result. Camp. ScieiU. Albert I" de 

 Monaco, Fasc. xxvi. pp. 39-42, PI. ill. figs. 45 — 50. 



t Viz., his figure 50 ; fig. 49 represents probably a central plate of an abnormal character, as Vayssiere 

 himself also believes. 



