GENUS CERATIUM, 457 



Examples of this species, having an average length of i-ioo," are abundantly 

 contained in the sample of surface skimmings from Fano, in the Adriatic, collected 

 by Count Castracane, and placed at the author's disposal by Dr. Wm. Gray. In 

 some, but not all instances, it was observed that the surfaces of the horn-like 

 processes were distinctly serrated. 



Ceratium seta, Ehr. sp. 



Cuirass bicornate, resembling C. fusus, but longer and more slender ; 

 body fusiform, slightly inflated centrally, the anterior portion of this region 

 notched, its posterior one tapering gradually into the basal horn-like 

 process ; both horns slender, setaceous, straight, or lunately curved, their 

 extremities truncate, their surfaces roughened or asperate, the front one 

 mostly the longer, often three times the length of the body. Total length 

 1-120" to 1-72". 



HAB. Salt water : Adriatic, with phosphorescent water. 



Ceratium trichoceros, Ehr. sp. 



Cuirass with three elongate, setaceous, horn-like processes, the single 

 posterior process straight, truncate, over six times as long as the ovate or 

 subglobose central portion, the two anterior ones recurved, obtusely pointed, 

 exceeding eight times the length of the central body, all distinctly asperate ; 

 equatorial groove obliquely directed, parallel with the anterior border of the 

 cuirass ; colour yellowish-brown. Length of body, without horns, 1-864" '> 

 total length 1-120" to 1-96". 



HAB. Salt water : Adriatic (September). 



Excepting for its minute size, this species, briefly characterized by Ehrenberg in 

 the ' Monatsbericht Berliner Akademie ' for the year 1859, does not appear to differ 

 materially from the slender-armed variety of C. tripos previously recorded. 



Ceratium longicorne, Perty. PL. XXV. FIG. 26. 



Cuirass bearing four horn-like processes, of which three, one longer 

 median and two shorter antero-lateral ones, are produced from the anterior, 

 and one long median process from the posterior segment ; entire surface 

 of cuirass and horn-like processes finely and evenly asperate ; a red eye-like 

 pigment-spot frequently developed at the anterior extremity of the body. 

 Length 1-120" to 1-90". HAB. Fresh water. 



This species, while first associated by Perty with the above-named title, was after- 

 wards identified by him with the Ceratium macroceras of Schrank, and under which 

 designation it is figured and described in his ' Kleinster Lebensformen,' in the year 

 1852. That name, however, so closely approaches the previously introduced 

 C. macroceros distinctive of the marine three-horned variety so named by Ehrenberg, 

 that the retention of Perty's later title in the present instance has been decided on. 

 A characteristic feature by which this form may be immediately distinguished from 

 every marine or fresh-water representative of the genus Ceratium described in this 

 volume, is afforded by the profuse development of the horn-like appendages of the 

 cuirass, no other type as yet encountered possessing more than three such processes. 

 The distribution of the animalcule, as with various other forms of Peridiniidae, may 

 be described as cosmopolitan. First reported from Germany and the Bernese Alps 



