_Thysanotesta sagittula_ Nathorst. The type-specimen is a long and narrow seed, 20 mm. long, ovate below and prolonged apically into a slender beak, 8 mm. in length, which probably represents a micropylar tube; the beak bears numerous stiff hairs (fig. 506, F). The seed closely resembles a carpel of _Erodium_ without the horizontal part of the awn. There is no evidence as to the nature of the parent-plant but the species affords an interesting example of a Palaeozoic seed apparently adapted for wind-dispersal, or possibly the bristles may have served the same purpose as in the fruits of _Erodium_. Attention is called elsewhere[1060] to the frequent resemblance of Palaeozoic seeds such as _Thysanotesta_ to fruits of recent flowering plants. =Carpolithus.= Linnaeus. Nathorst[1061] has pointed out that this generic name was employed by Linnaeus for fossil fruits: in the form _Carpolites_ (Sternberg) or _Carpolithes_[1062] it has been widely used and differently defined by authors, usually in a comprehensive sense including fossil seeds from both Palaeozoic and Mesozoic strata which cannot be assigned to a definite position in the plant-kingdom. It is desirable to adopt some designation for seeds from strata of different ages which do not exhibit any features sufficiently distinctive to justify the creation of a special genus. By employing such a name as _Carpolithus_, without attempting to define its characters within prescribed limits, for casts or impressions of seeds which are not distinguished by any striking characters and cannot be allocated to any particular section of seed-bearing plants the unnecessary multiplication of generic titles is avoided: when any additional data are obtained differentiating particular types from other forms of _Carpolithus_ the provisional term should be superseded by some distinctive generic name. Among seeds from the Coal Measures there are several examples of both large and small types without any regular ribs or lacking such features as serve to distinguish the genera already described, which are appropriately included in _Carpolithus_. The two species _Carpolithus Wildii_ Kidst.[1063] and _C. bivalvis_ Goepp.[1064] are two examples of seeds from Upper Carboniferous rocks which it is desirable to refer to this comprehensive genus pending further discoveries as to their morphological features. The Jurassic species _C. conicus_ Lind. and Hutt.[1065] is another type which it has been customary to include in _Carpolithus_. (_Microspermum._ Arber.)